5'11" and 110 pounds?

I'm a male and 22 years old. I have tried everything to gain weight and nothing has seemed to work. I have never eaten properly since I was a child only eating one small meal a day sometimes nothing just depends. My eating problem has progressed so far that I even forget to eat, my stomache won't growl,I don't feel any fatigue whatsoever so it just slips my mind after a hard days work. My doctor has tried his best by giving me anti-depressant medications to make me hungry but to no avail. If i eat more than once in a day I feel terribly sick, I don't throw it up or anything but i'll writhe in pain from severe abdominal pains and cramps for hours. I do have celiacs so i'm used to the cramping from that and its not the same. Everyone just tells me "well start eating" its gotten to a point where my family and friends are agitated and hostile towards me thinking I can just magically change but its far from that easy. I work in an acute care hospital and have been doing in home nursing care for years as well so I am well aware of the effects it can have on my body. I need help. What is a good method to help me get to a more normal weight? An excercise of stretching my stomache maybe? Any advice will be greatly appreciated!