I am a decade+ older and in the winding down stage of the second marriage. I was where you were after the first marriage and am coming back to the same place because I jumped into the second one too fast. I also had a serious burnout/depression and spent 3 months medical digging myself out of it by reading the psychology literature and looking for help in many places, some unusual.
So, I am going to say a bunch of things that helped me. The challenge is that maybe they will not seem helpful from exactly where they are, because they may be two or three steps ahead of exactly what you need. But, if the stuff resonates, let me know and I will be happy to give more details over the email. The most important point is, there is a way out. And there is a lot of resources out there to help you to find the way out. But you need to take ownership over it. In the way that works for you. Which is catch-22 right now because you are overwhelmed. But maybe something below will help you to find a direction you can move in and then you add the rest.
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Psychiatrists do not make you better.
They get you back to the societal mean. At best. Psychologists may or may not make you better. Actually, they do not make you better. They walk along with you as you make yourself better. They are "the tool" not "the leader". Which opens up a question of whether they are the right tool. I looked at maybe 30 different psychological approaches trying to figure out which one was for me. And, nearly accidentally, discovered John Rowan, who wrote a lot of books on therapy, personal growth, etc. And deep in one of the books, there was a table which split personal positions and therapies into four categories (columns). The table blew my mind. I think it was in the book Personification (ISBN: 9780415433464).
It says that people may be in one of four major places. In first column, they may identify and judge themselves against society and its norms. That's where psychiatrists and psychological approaches like CBT work.
In second column, they want to redefine themselves (I want to be the kind of person who does X - e.g. cooks fancy dishes). So, they have internal resourcing and internal guidance. Gestalt therapy works in there.
In third column, they believe not in society but in external entity. God, angels, tarot, etc. Jungian approach resonates for those people, but so does Tantra, etc.
And, in fourth column, there is non-dual people. Taoism, some Buddhism (Dharmakaya, not Nirmanakaya).
The point is. Do you know which of these are you? I am column 2. And when I understood that, it became easier to see when something was aligned to my solution path and when something was "trying to help" but was using a terminology that was very misaligned to my internal process.
I am guessing your definition of self was coming from your partner before. And now you are still aching for that definition, but it is not available. So, you have roughly four options:
1) Find another source of definition of you, given to you by external sources. New partner, workaholism, group that will gladly take all of your time. That's column 1 solution.
2) Decide to figure out who "you" are. Basically, The Ship of Theseus approach. Decide that "I am the kind of person who is .... (great home chef)" and then do whatever is needed to become that. That's a lot of soul searching. And a lot of scaffolding building. I am doing this right now. I found Existential Therapy approach helpful to think through that. I found Sara Kuburic's book (It's on me, ISBN: 9780593449264) surprisingly good overview for that, as I prefer to do deep work myself. Victor Frankl is existentialist, but I did not find his book that useful, I think the therapy modality that is built on top of philosophy is way more relevant.
3) Decide to lean on external non-societal authority (column 3). Go find a Pegan group, start looking at Astrology, wake up your kundalini snakes, etc. Maybe it will resonate, maybe it will not.
4) Go all Tao or Zen or "it is what it is".
There is a little bit of a cheat. A lot of healing work happens in column 3 spaces. But you need to either resonate with them or find a translation layer to be able to participate. I've been building the later for myself, but it is even more work. Worth it, though.
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You do not know yourself, yet. You need to build your interoception. You need to ask yourself a question of "is this interesting to me" and being able to feel the answer. This may feel strange but it is totally doable. You can start by trying to assign numbers to your anxiety strength on any particular day (I have 1-10 scale with breath stop at 11), but it can get way more nuanced. And the deeper you go into interoception, the more clarity you get. Meditation is one (long) way to go there. But, something like Gendlin's focusing is another. There are some groups online that practice Focusing, some even for free.
Also, Authentic Relating, Circling of various kinds, Ann Weiser Conrell free mini-courses, etc. You could be busy online "present" with people every day of the week.
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You may need to grieve. Or some sort of cathartic release anyway. Again, a bunch of ways to do that, you just need to search for them. Sometimes in weird places. Ecstatic Dances are one way people do that (5Rhythms, etc). Holotropic Breathwork is another. Some online breathing groups, too. Look for groups that are present somehow "as they are", often with music.
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You may need to rebuild social skills and/or play test different personas. Improv is amazing for that. I know a bunch of people with depression or anxiety growing and chilling-out through Improv. That also gives you community. And quite valuable skills (hearing what people actually say; or, on advanced levels, what they don't say). It is a lot more than what it promises on the tin.
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Journaling, especially writing things by hand is very useful. Could be morning pages, could be Progoff's Intensive Journal, could be deep chat with LLM. The reason it works is because when you just think those thoughts, your mind compresses a lot of little steps or even skips them. It runs right past the open doors. When you write them out line by line, your brain both reads what is written and - importantly - stops holding on those thoughts too much, because it trusts the external capture. Even if you then burn that peace of paper.
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I did not touch sexuality and sensuality. Not for this site. But, let's just say, there is a lot out there as well, of all kinds. Not just Tantra.
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There is more. Lots more. A bunch of that is in old books from 1970s on archive.org for free. Bunch of it is kind of 303 or 404 level, you need to get 101 sorted first before you understand the concepts. Rituals, liminal spaces, positive effects of placebo, proximate zone of development, the rabbit hole can go very deep. And, it all can be healing when you have sufficient scaffolding for it. The scaffolding is the key, you need to build it for yourself.
The overall point is, there are many paths forward. You are on a threshold of starting to walk one or more of them (Asking HN is a sign that you are getting ready). Don't see "right now" as a terrible time. See it as an opportunity to figure out who YOU really are, and get that solidified before the next relationship. It is hard work, but it is worthwhile work. I did not do that around your age, and I am back at the ground work point again. I can't stress this point hard enough.