Can it be gerd? What should i do?

Iam 20 years old. I drink a lot of coffee. Sometimes i drink more than 5 cups a day. I knew i had acidity for a long time. I always had stomach burning and sometimes wet burps. But recently for the last three months , i lost weight and im feeling very tired. I feel like im losing muscle mass but my weight is not decreasing. It decreased only once. One day i had black colored stools and vertigo. From then i keep having the symptoms including  cold sweats, vertigo, dry mouth, loss of appetite and cravings , vision problems, and going to the bathroom after i eat with foul smelly stools. First i though it could be hiv. My exposure was 8 years ago . i toom three hiv tests this month. Tridot , western blot and pcr. All the three wee negative. I have consulted two docs in person who say nothing is wrong. But im symptomatic. Dont know if its anxiety or some underlying illness. What should i do?