infertility??

So I am 21 and I don't have to worry about having kids for a long time but my periods are always really far apart and the cramps are absolutely terrible. I am also in my senior year at college so this might be cause by stress but I can't help but to worry that I might be infertile. Like I said, not something that is a priority right now, but I don't want to be surprised in the virtues. Thoughts? Advice? Anything to just put my mind at a bit of ease?