Yesterday I spent all day inside on the couch, being very inactive. I was not hungry at all and barely had anything to eat, but I felt fine. Today I had plans to go for a run and I know from experience that if I don't eat and drink well before exercising I easily get dizzy and feel close to fainting. So naturally I made sure to eat plenty this morning to avoid this. However, I became pretty nauseous and had to throw up. After coming back from the run I tried to have lunch but I had a lot of trouble with it. I did manage to keep that in though. I'm a little worried now because I am still not hungry at all and don't feel like eating anything, and have skipped dinner because of this. Could this be because I'm on my period? I've never had this before (I'm 19). I don't take any medication or have any other health issues, but I do take the pill.