I m 21 and am currently menstruating, but this time is very different. To preface - I was underweight as a child and a very serious athlete before and during puberty, so I m used to 3-4 extremely light periods per year, tops. I left my sport in February, had three periods between then and now that were like my previous ones. This time, however, I have a headache and am feeling very nauseous. I understand that I may just not know what my real period feels like, but I want to be sure it s not something worth a doctor s appointment for.