Struggling with Anxiety Medication

I have been on this medication for 2+ years now and everything was great! Until I left for comment my anxiety got so bad, I tried to switch medications but that made it worse and ended up going back to Effexor but left college to do online at home. Now I visit a couple times a month but I really just wanna go back to the old me and be ok again. Why did I all of a sudden have panic attacks. I couldn’t sleep, eat, etc when I had anxiety all day. Didn’t wanna get up or go to classes. Nothing helped besides fresh air or a hot shower. I would go to the bathroom and just water would come out because my nerves were so bad. I finally left and now I’m on 150mg of Effexor but how do I know this is the best medication for me.