GI Specialist won’t change my prescription, in constant pain

Hello, I am 18 years old and have been diagnosed with GERD. I have been suffering from it for around a year and a half to two years. It started with a simple flair up that was easily aided by taking a Pepcid. I had a flew flair ups that were also taken care of by Pepcid until eventually it just stopped working and I was in constant pain not helped by other methods (zantac, tums, natural remedies). It was like that for a couple months and then eventually went away without any particular reason I can think of. The pain that I got that was the worst of it was gone but I still couldn’t lay down at all without pain. Eventually, it came back at around the beginning of August. It lasted for about 3 weeks of dread trying anything to fix it and then eventually, I started taking omeprazole which pretty much instantly gave me relief. That lasted until around the end of October/ the beginning of November. During this time it definitely got the worst it has even been, I couldn’t sit at my computer chair, or even think of sleeping on my bed (regardless of whether I was laying up or not), and I could only really sit/sleep on one spot of a specific couch which was a corner spot that I could put my arms up on while sitting up and I guess this helps me somehow? Anyway, I was in constant pain that was pretty much immobilized me and took away my life. When it came back again at the end of October/beginning of November I tried taking omeprazole for another 2 weeks, my symptoms didn’t get better at all through that course of time, and I went back to being hopeless. Around November 20th or so I went to a new doctor to get new medicine, and she prescribed me protonix 40mg, which helped mildly but I could still definitely feel the symptoms, especially after I ate, or sat down anywhere other than the seat I mentioned earlier. Although it wasn’t fully healed, I was definitely feeling better until I went in to get an endoscopy done to see what was happening. They didn’t find anything, but it did make my acid reflux come back again. Somewhere along the line I was prescribed sucrafate and started taking that after the endoscopy, still no symptom changes. I contacted my GI specialist and he said that he wouldn’t change my prescription because it was what I was supposed to be on. I’m frustrated, sad, and hopeless because I’m going through this pain with no change or relief from the medicine I’m taking and there seems to be nothing I can do about it. I’ve been taking Protonix 40mg for around 37 days and I’m still in pain and I don’t know what to do. My back hurts from sleeping sitting up since August and I just want to be a normal 18 year old again. I’ll list some of my details in case that helps at all. I have lost around 100 pounds since February 2017 and am sitting around a healthy weight as of now. My diet is plant based as in I don’t eat any animal products. I used to not eat any oil or premade foods (to lose weight) but I recently started eating those again during the holidays (symptoms are the same with or without consuming those). I used to walk around 20-30 minutes everyday but stopped after a while (not sure if that could be a reason for my acid reflux flaring up again). Any help or insight would be appreciated and feel free to ask me anymore questions if needed.  Thank you. 

Did you do a biopsy with your endoscopy to check for H pylori infection?

Yes, and that was negative.