The Depo shot.

I am 18 years old. I got on the shot over a year ago. I have sometimes severe back and knee pain and headaches that can put me down. I have not gained any weight with the shot, my doctor actually said that I have lost weight. I eat ALL THE TIME. Sex...well that has not been so fun for me lately, and its not my partner. And I get god awful pains when we have sex, which makes it even worse of a time. I enjoy having sex so that is a problem. I always have to go pee, and I am always always thirsty. My acne has gotten even worse and nothing will make it go away.
I am scared to get off the shot because it is so convenient for me, and I am not very good with taking medication. I have recently discovered something about my body that scares me to the bone. I have gray hair all over my head. That is not a normal thing for an 18 year old to have. We are making an appointment for friday, BUT i am just really looking for someone to help me. My doctors are dumb. I just researched the side effects of the shot, because all these things are wrong with me and the doctors can not figure out why it is happening, so i put two and two together and I think its all from my shot. But the gray hair thing isnt listed anywhere. I need advice...different birth controls that are strong and effective and safer.. please