I find that when I have anxiety about things or people are unsure of things, it's always important to drill down into the 'why'.
"Why am I doing this thing I'm anxious about?"
If its because I have to for adult reasons or some other goal and there's no better alternative, then I just suck it up and do it, it's not gonna get any easier.
If its because of societal expectations I ask myself "Do I care about conforming to this societal expectation? What will it cost me if I don't?" and then I go from there. If I truly don't care about it, but it will cause issues later, like flaking on an event and then friends won't invite me if I do it too much, then I'll decide that the cost outweighs the amount I don't care.
In the end, it all comes down to identifying the 'why' for me and then doing a cost-benefit analysis of the tradeoffs of: 'how much do I care?', 'what is the cost of not doing it in terms of money, stress, or societal expectations?', and 'is there a different option, if so how do the costs compare?'.
In your case, I feel that you are doing this because you think you need to get better and all these other people know things you don't, and you don't want to look stupid. You need to decide if you even care on all that.
I had the desire to learn and get better cause I always felt behind before as well. I don't know if it quite manifested as learning anxiety, but I had some things that helped me. I knew that while these people knew more about Mathematics or more classical computer science things, I had other things they didn't such as knowledge of foreign languages and cultures, or I wrote better code from a readability/maintenance standpoint. I'm sure you have some other piece of knowledge they don't even if its something like world history. It may not seem useful or applicable but every piece of knowledge can be applied in some other context some way, even if its just realizing that the problems are similar so you know to look up how it was solved previously in a different domain.
So step one is stop comparing to them. Step two is to sit back and decide if you actually want to be learning these things, and why. Step three is deciding which things are going to be the most immediately applicable, and if you need to learn something first to learn it, then do so(learning algebra to learn calculus). Step four is moving on to the next thing after you have that to a good enough base knowledge.
You don't have to be an expert in any fields here. Just get to a point where you can easily learn more. I imagine you can most likely do two new tech domains at once as long as they aren't too similar, but don't bite off too much. Just do at least a little bit of study a day. Even some more boring technical books that are 300 or so pages can be tackled in a month at 10 pages a day! But don't stick too hard and fast to things like that. It might be easier to do a 5 page chapter now, and then a 15 page chapter the next day. Stopping points like that help. Also if you read too much you could affect retention.
Look into some things about learning techniques such as spaced repetition stuff like Anki or Supermemo. Things like that pay dividends by making you spend less time overall and you won't need to learn the same thing twice if you keep up with it. Gaps in studying can be bad cause you don't progress but you also regress at the same time, you can see that after semester breaks in school when you go to the next level of class and everyone forgot half the previous semester. The worst thing than a gap in studying is a longer gap. A one or two day gap sometimes is no issue really but a month is, and three months is worse! Habits make perfect. Some analogical advice from my time as a recovering alcoholic would be this:
"Stumbling and falling down looks dumb in front of everyone and it's embarrassing and it sucks. No one is denying that. However, not getting up and just continuing to lie on the floor looks even dumber, and you'll be in people's way. Get up and keep on walking and eventually you'll learn how to not stumble anymore, or if nothing else most of your time at least won't be spent on the floor."
I know this is a lot of stuff to think about and so I'll make a quick little TL;DR.
1. Figure out the 'why' and if its worth doing
2. Figure out if there's a better way
3. Figure out the best way to do it