under sedated for upper GI endoscopy?

I'm not a medical professional so I hope I am allowed to ask for advice here. I lived in Ohio my whole life and am 29 years old. We just moved from Ohio in late August. Mid august I had an upper GI scope to check for ulcers, etc that are causing near constant nausea and bad heartburn that never ends. I went into the local Endoscopy/Colonoscopy center for my appointment and filled out the paperwork, etc. When I was sedated for the scope I really felt it nearly immediately. I was having trouble forming words, etc. The doctor got ready and started the procedure. I knew it was bad when I started gagging uncontrollably, it hurt like heck, I felt the metal tube scratching my throat. It hurt like heck when he went from my esophagus into my stomach, it seemed like he had to push hard to get into the stomach. This whole time I am gagging so badly and belching uncontrollably. Tears are flooding my face, I felt it was hard to breathe and at that point I was panicking. How could you not??!! I was totally fine beforehand, no anxiety other than the general uneasiness with a new procedure I had never had before... It took at least 15 minutes for the stupid procedure and come to find out later he never took biopsies! None! I am ticked and feel so violated and scared of procedures like this now.

I was working on getting a Celiac diagnosis or find whatever it is that is causing my neverending nausea and diarrhea. To go through that horrific living nightmare and not find out anything I didn't already know is absurd.

I was told I would not remember a darn thing from the procedure. That was an out and out lie.

I will likely call the gastro center and request they mail the full report to me as I need to know why it didn't work. What drug did they use to "sedate" me, what my blood pressure was before, during and after the procedure, etc. All I know is I kept falling asleep after the procedure in the recovery room and the stupid o2 meter kept going off because my 02 went too low. *sigh* It was one heck of a horrible experience.

Yes I am very obese but honestly that should never happen! It's been 7 months since the procedure and when I remember having it done I am almost in tears because it was so awful.

I will likely have another one done this year and need to know how to communicate with the medical staff so that they can fix whatever it was that happened last time so it doesn't happen this time. Since I am now in a completely different city and state I don't have easy access to just go to the medical center and talk to them about it.

I really am traumatized by it. What should I say to the medical staff when I have this done again?