Nauseated for a year!

For the past year and a half I have been on Lexapro for anxiety. Then in late November of last year I started getting nauseous a lot. It was on and off for a few days then I started having other symptoms like diarrhea, bloating, and stomach pains. I thought I had some sort of stomach bug at first. I could hardly eat without feeling nauseated. Then in January of this year it hit me really hard for two weeks. I was out of work it was so bad. I thought it might be a stomach bug again but this time I had all of the prior symptoms plus I was vomiting and could not eat or drink anything without getting sick or having diarrhea. I lost almost 20 lbs in 3 weeks. I knew I would get dehydrated so I just delt with the getting sick part after I sipped some hot tea that I was hoping would help calm my stomach. (it didn't)
My doctor sent me for a sonogram of all my organs and a HIDA Scan. Everything came back normal. She then referred me to a gastrointestinal doctor who then proceeded to do an endoscopy and colonoscopy. There was inflamation (inflammation) and a couple polyps but the biopsy's came back negative. I was put on Nexium for the inflamation (inflammation) for 3 months. All the while I was still having all of these symptoms only now I started getting headaches more frequently, I do suffer from migraines so I tried to treat the headaches quickly so they wouldn't turn into a migraine. Most of the time they didn't but I was having at least 1 or 2 headaches a week. After the 2 GI tests I had a Hydrogen Breath test and completed an elimination diet. We found out that I had a bacteria overgrowth and that I was lactose intolerant. I was put on a med for the bacteria to clear up for 2 weeks.
After that I felt good for a few months and now I'm back starting to have the upset stomach, headaches (more frequently this time), nausea, diarrhea, the chills and sometimes I can't stop myself from shaking (like I was cold). The GI doctor said that we need to treat the symptoms while we find out what is causing it. So I'm on Compazine for the nausea which helps a lot.
I think this time it feels a little different then what i was going through before. Most of the time the symptoms happen at night before bed or just a little while after I've gone to sleep. I then spend the remainder of my night and wee hours of the morning in the bathroom until I spit into the toilet enough to where my mouth and throat go dry so I hope I won't get sick or until the diarrhea has passed. Whichever comes first. I have a high stress job, 3 kids, a husband who now has been sober for year, and I'm taking care of my mother as well. I'm only 28 years old but I feel much older and weaker. The overwhelming feeling is starting to come back and I'm more emotional now as well. I feel like I may need something stronger then the Lexapro. In the past year I've went from a size 18 to just about a size 12 now and lost 30 lbs. I'm not complaining about being a little smaller but it's just the way it's happening that's annoying. I've missed so much work from feeling ill all the time. I've thought about trying to either take a demotion at work or switch jobs but I can't afford to do either. Someone please give me any ideas of what I might try! This has been very dibilitating and I'm just so tired!