Will my doctor be able to help me?

I am a 19 year old female that is 5'6" and 156 pounds. In January I was about ten pounds heavier but got food poisoning so I lost that ten pounds in the three days of not eating. Since the beginning of January I have been running 20-30 miles a week and doing a little bit of strength training. Nothing has changed other than my body developing a little (very little) more tone. I don't know what is wrong. I haven't begun eating more than I was before I started working out and I don't eat crazy amounts of food either. I am going to go into my doctor because I believe something must be off. The only thing that I can think of that might be related to this is that randomly I get really cold when it is not even that chilly. Will my doctor be able to tell me anything useful? Do I have something wrong with me? I don't know what to do. It's very discouraging.