Digestive problems. Do let me know.

Symptoms: Having pain in stomach, nausea, constipation and vomiting It's been 2 to 3 yrs I am having the issues and in reports everything comes normal and I am unable to understand what is the issue with me. I will be ok till the time I had medicine but after some time the medicine also don't works. I eat a lot then also I go for the motion after 2 or 3 days, having digestive problem. I am unable to brush my teeth also, I start vomiting. I have to take medicine to stop vomiting but that also didn't work due to which I face the issue of low blood pressure. I don't know what to do how to deal with the situation. I don't eat street food or fat related item then also I am facing such issue. Please if any Dr knows what is cure and treatment of my problem do let me know.