Help me get motivated to loose the pounds?

A year ago I was hospitalized from loosing half my blood and had to get 3 red blood cell transfusions. I lost this much blood from lady problems from hemorrhaging. To stop the bleeding my parents had no choice but to put me on depo so I wouldn't bleed to death. This medication causes some people to gain up to 100 pounds.. After I got out of the hospital, I had to get surgery. This was April of last year and I've gained 15 pounds of which I wasn't comfortable with my body in the first place before I gained it. My mom told me that I'd be able to loose it after I had my strength back of which I got back but then found out that I had endometriosis and now my doctors think I have IBS or something to do with my intestines but they are both very painful. Also I have hemophilia (hence the almost bleeding to death because hemophiliacs can't stop bleeding once they start). Anyway, I'm depressed and can't find the motivation to do anything, even loose weight which is making me even more depressed than I already was about my illnesses and how painful they are. Please help! I'm only 15 years old and I don't want to be like this forever