ok so i've been having very long periods, about maybe two weeks? they also are about medium when it comes to how heavy it is. and the time in between before i start my period again is about two weeks as well. I don't know why i am so irregular and it worries me because i am losing a lot of blood when i am pretty underweight. but i heard exercise can effect your period? i am a runner and i run about 5 miles a day. but i read that exercise is what can make your period go away for a while, when it is the complete opposite for me. should i go see a doctor? what is wrong with my periods? please help i am very worried for my health :-(