Therapy for you, NOW. Do not let yourself get trapped into the fear/paranoia cycle any further. It will absolutely destroy you, and take your life with it if you let it. TBH, BF needs therapy too, if he isn't receiving it already.

You need to have a conversation with your BF, because he shouldn't be letting his friends trash talk you. BF needs to tell them, and doesn't have to go into specifics, "I'm on a medication I can't mix with alcohol." He also needs to speak to his therapist, because drinking is not a requirement for going out with friends. I too take antidepressants I can't mix with alcohol-but go out for "drinks" with friends all the time.

Lastly, you need to work on balancing the You+Me=Us equation. You're putting almost everything in the Us side, and not taking care of you. Ideally, you need to be 50/50. Rediscover lost hobbies, or try a new one. Take a new class in something you're interested in. Have a regular exercise routine-even daily walks are fine. Do a fitness challenge! If you've always wanted to try a fun form, like yoga, Pilates, Zumba, spin class, stand up paddle board, surfing, etc-find a place that offers lessons or classes and do it! Always wanted to try a musical instrument? Take some lessons!

Spend quality of time doing self-care and nurturing yourself. Think of your relationship like a house. The house is important-but the foundation of two people that are doing well in life is the foundation on which it is built.

I did almost exactly what you did OP. It led to a mental breakdown, and I nearly lost everything-friends, family, my relationship, and my life. Please don't make the same mistakes I did.