After years of diets I literally feel sick all the time?

I'm a woman. I've done atkins, zone diets even vegetarian eating for a while. Now I'm not fat but I don't look thin either. My body seems that it doesn't changes at all. It changes really slow. I'm tired all the time. I have stomach aches,gas problem, headaches, I feel cold easily. I also feel like I need to sleep many hours. I have runny nose and sore throat everyday. My skin one day is oily the other extra-dry.Lately I try to eat balanced and take vitamines (and stopped coffee) but I have a really bad ache to my bones (neck, back and knees) I'm trying also to walk a few miles every week but still it's like I'm always sick. What should I do?