Seek professional help. There's no shame in having somebody to talk to about things like anxiety, and they are there for you. I stress professional. You're probably going to have to pay for it.
I continue to see somebody regularly for my mental health, been going over 15 years now. It's a cost, sure. But so is gym membership.
It's hard sometimes to just let people be "people" and not sexualising the work relationship is very important. This is a fast path out of a company. You'd be sacked for cause in an instant if somebody complains.
Don't let this rumble along. "Man up" and deal with it. Life is better if you face up to mental health issues I assure you, from personal experience.
Some employers have schemes to help. You need to be circumspect finding out if your one does, because asking HR can have negative consequences even if this is strictly illegal. My employer had signs up in the coffee rooms and toilets. If you have work provided health plan it will have a component for mental health and you can ask the health provider whats available with some assurance of confidentiality.
If you're being bullied there is an HR path for help which does not have to raise the obsessive sexual thinking issue, and when you get to a competent mental health professional you could maybe raise it there.
Good luck. Look after yourself.