Hi I am a 24 year old female I got my period at a very young at 11 I use to bleed for 3 weeks and have a week break in between so at the age of 12 I visited my gynecologist and he out me on the pill.my period was regular so I stopped it after a year then I started to bleed for 3 weeks again and have a 1 week break so I went back on the pill and then stopped it at the age of 21.now I hardly get my period .I get it like once every 3 months and around my period time I get so severe cramps and when I do get my period I bleed for 2 and half weeks. I also can't fall pregnant. I am also a thin female 49kgs.what could be the problem