Like I'm dying: Nausea, stomach pains, body weak, flushed, wt loss

i am a healthy (I thought) 43 year old female. 2 weeks ago I was at work. Stood up. Got this pulled muscle sensation in my back around my bra strap area. I then proceeded to have chest pain, shortness of breath, flushed, sensation of hot liquid seeping out into my chest, dizziness, and numb and tingly all over my body. I felt like I was gonna pass out or die. I was rushed to the ER. After several tests, and an overnight stay, they discharged me the next day with Synthroid (thyroid just a tad low) and Flexeril for my back pain. I still had the shortness of breath. But they assured me my heart and lungs were fine. Did not do any x-rays or anything for my back. The next day I was pretty much laid out at home due to the flexeril. The following day, I decided to go back to work. Got up, took a shower, then I started having all the same symptoms as before. I had my son take me to the ER again. They did several tests, said my heart and lungs were fine. The doctor diagnosed me with GERD, and sent me home with Prilosec. I took Prilosec for 4 days, then my PCP had me try Protonix, which by the way, both of these gave me horrible side effects (confusion, delirium-hallucinations) and were not helping my stomach pain and nausea. So, she started me on Zantac, which worked wonders the first couple of days, but seems to have worn off now too. Also, after numerous testing, doctor said my Vitamin D was low, was 11, and should be between 30-80. So I started taking Vitamin D3--400 units. 2 weeks later, I have been to the ER three times, had an endoscopy just yesterday (doctor said everything looked fine, but sending off stomach sample for biopsy). Still taking Zantac, and Vitamin D. Trying to eat more foods rich in Vitamin D and calcium. I continue to have nausea, stomach pains, body very weak, losing weight, diarrhea, dizziness, flushed and feel like passing out. I can't sleep, and feel very dehydrated. Every morning I feel like I'm dying with these symptoms. It feels as though it hurts from deep inside my muscles or bones, even my joints in my fingers and elbows hurt. Closer to noon, I feel a little better, try to eat a little something, then it starts all over around 9 or 10 in the evening, and keeping me up all night. I WAS TOTALLY FINE UNTIL 2 WEEKS AGO, THEN ALL THIS STARTED HAPPENING. CAN SOMEONE HELP ME PLEASE? I DON'T KNOW WHAT ELSE TO DO. I FEEL LIKE I'M JUST GONNA SHRIVEL UP AND DIE.