A little backstory... I've been on Sertraline for about 6 years, most of which was spent at 50mg. Being on a 50mg dose took the edge off of my anxiety and panic attacks, but I always had that uneasy feeling and anxious that would come up...I didn't communicate this to my doctor until September of last year, for no reason other than I don't typically share well... Anyway, after telling him, we increased the dose to 100mg, which took that feeling away, but rendered my dick bubblegum... So I told my doctor immediately, because the best motivator for me honestly is sex... I've always had a crazy high sex drive and no matter the dose I never lost that drive.... So the drive is still there, but my dick decided to take a  sabbatical without informing the rest of me.
   So I tell my doctor, he says it's normal and I believe him, and he prescribed Bupropion... Which slowly worked over a period of a couple months, going going from having sex with half hard sponges to a decent erection, very useable... But never rock hard.
  Then recently, I don't know what happened but I had a panic attack in the middle of sex with my girlfriend... Which I have to say she has been amazing and supportive through this entire thing. I couldn't ask or dream of anyone to be more lucky have at my side than her. Since the episode, I'm now constantly in my head about ever being a good lover again to her...I love her so much and I hate that I'm putting her through this... With my sex drive we still do everything, but like my dick will get hard through masturbation, but the second there's the least bit of "hiccup" during sex (position change, awkward hole miss, anything uncomfortable, etc...) my dick instantly goes soft and bails due to my thoughts of "It's happening again" or " I'm a disappointment", even through I'm crazy turned on.
My girlfriend and I have great communication and share... But it's like no matter what she says or does,I can't get these thoughts out of my head.

Mentally I'm a mess now and physically I'm incredibly sexually frustrated.... And I have no idea what to do.

Edit: Oh I forgot to mention... My doctor and I have listed the dose of Sertraline back to 50mg and kept me on the Bupropion 100mg.