I think i'm infertile because my periods have stopped and, I am 19.?

Last year (09) I think I had my period about 4 times. I haven't had my period since the end of September. I was laying in bed wondering about why this could be, and it struck me that maybe my ovaries have stopped creating eggs? I don't really know about this kind of thing. I live with my Dad and I really don't want to talk to him about it. Does this mean I'm infertile? When I first got my period it came pretty much on time- I was 12, but for the last couple of years- and especially lately, i have hardly had it, and when I do have it it only lasts 3-4 days. Am I infertile?? I eat plenty of food and I weigh 54 kgs and I am 154 cm