Ive been having problems since around early November.

I get excessive bloating and fullness, often combined with nausea and even shortness of breath because I feel so full. Ive lost about 20lbs in two months because I have a very difficult time eating since im constantly full.
Ive had very little pain, the VERY few times I did it was only gas and very mild. No vomiting either. Several times ive felt like vomiting but I never did, a few times ive actually been in the bathroom TRYING to vomit for a few hours but nothing ever comes out... usually after 3-4 hours I feel like somethings about tome come out then I just let out a HUGE burp and somehow feel a bit better.

Ive had a bloodtest, an ultrasound of my entire abdominal area and even an endoscopy.
Everything shows to be fine. In the endoscopy they found some mild gastritis in the stomach lining but it shouldn't be causing such extreme symptoms.

I feel like I have food all the way up to my neck, some days it's a little better but on the bad days I will drink a tiny little cup of water and get SO full that I even feel short of breath.
On the bad days, which are pretty often, I can't even leave the house b/c I feel so nauseas and uncomfortable.
I just started a parasite and Colon Cleanse to see if that could be it, only been on it a week and it's really loosened me up as ive had diarrhea all week on it (using parastroy and Oxypowder by the way). Im also on protonix to heal the gastritis, been on that for about a month, not that it's doing anything though. Im sure it's healing the mild gastritis but that's not really my problem.

I didn't have any warning signs leading up to this. The only thing I did notice was that I was slightly constipated, I was going once a day but considering the amounts of food I was putting in (im a bodybuilder so it was all clean food, but quite a bit)there wasn't as much coming out. Aside from that ive never had any problems.

What can I possibly have?? I eat a small meal and feel like I ate a horse, then get very nauseas and bloated. I have no idea where to turn anymore