Talk to Gastroenterologist on Stomach

I have a strange stomach problem. Don't know if its allergy or IBS or ulcer. I have been having this problem for the last few years now. Consulted a few doctors too but the problems remains. It gets triggered after unsuccessfully passing of stool in the morning (but not every time); just like constipation; it feels like air is boiling up my stomach. Is followed by pain in the right portion of stomach immediately below my right ribs. It feels good to press on the pain area. Sometimes, eating something settles the pain, at others, I feel nausea and go to sleep (even if I have slept well through the night). Sometimes, even sleeping doesn't reduce the pain and results in excessive vomiting (there are usually 6-8 vomits with intervals even if I'm empty stomach. I usually do not take meals after 8:30 pm, I'm not overweight, I avoid spicy food. The thing that bothers me the most is the pain which is unbearable and travels to head. Sometimes, taking arinac settles the issue.