I get sick after I run...?

I am in conditioning for track season right now. I am only 16 and I get really sick after running. I usually run 3 miles after a school day and after the 2nd mile I throw up like blood and bile. It kinda freaks me out but I just tell myself that is happening because I didn't eat all day. I only eat very little during a school day. Is that why I am throwing up that stuff??