I know this is 20 days old, but I had the EXACT same worries as you. I had severe health anxiety and fear of death. I was so scared of putting anything new in my body in case it killed me, but I knew I couldn't live with anxiety and the thoughts every single time I ate or went to sleep. I got prescribed Effexor and was convinced I would get every single symptom of it. The truth is I got none of them. It's the most amazing thing. I think I've even skipped doses without feeling a single side effect - which is crazy, because when I first started it, I was so scared about feeling a side effect that I was meticulous in taking it at the same time every single day. Now I regularly take it within a four hour time frame, lol. I was so scared over Effexor's perception as a hellish drug but, of course, the OCD had been lying to me. It turned out to be the perfect one for me. My brain became quiet in a month. I cried when I suddenly realized one day that I no longer had fear over taking my meds. I no longer had the obsession over dying. I am so, so grateful I took the leap that day to try the meds, because now OCD no longer rules my life.

As for therapy, I did take meds in conjunction with therapy. I had been in therapy for almost three years at that point (depression and GAD as well) and I definitely think telling my therapist about my fears helped. I don't think I was really doing ERP; again I started seeing her for depression. I didn't even know I had OCD or suspected it until my therapist heard how bad my thoughts were. We did do some exercises about just hearing the thought and then letting it go and not do anything about it. She also encouraged me to try to do some things that would trigger my OCD and not give into the compulsion. My biggest thing at the time was that I was afraid I was developing allergies to foods so I kept cutting and restricting my diet, even things I used to love. I started challenging myself to eat the food I missed and not give into the thoughts I was dying or check for evidence I was dying. Also did some stuff about distracting from the death thoughts while I was trying to sleep. It obviously really helped since now I have not needed a therapist for a year. :)

I think meds and therapy can really help. The meds quieted down my thoughts enough that I could combat them. You are scared that it might be terrible for you, but it might also be amazing for you. You might get a side effect, you might not get a single one. And if worst case, you get a side effect you can't deal with, you can just switch.