Why are my periods so weird?

Im 18 years old . I've had my period sine I was 14 . But about the past couple months its been really wired like comming twice and month , sometimes not at all . Evey single time I get it its at least 8 days long . Am I ok ? What should I do ? Also there is a lot or HORRIBLE pain [ cramps] that come with it . Not to mention the BAD temper and just being super tired . Help !!

I once read in a magazine that periods sometimes get really irregular if you are too stressed out. I also read that periods could last from 3-14 days sometimes, and it is all perfectly normal. And horrible pain is normal too. My sister once had to stay home from school because she couldn't even move because of the horrible pain of the cramps. And whenever I get cramps I feel the same way, and it seems like no kind of medicine could ever help. But if you feel that something is really wrong, you should talk to your doctor about it. But from what you said it sounds completely normal, just get lots of rest and un-stress yourself!