First of all, how long have you had your period? I know that if you've only had your period for a few years, then this is relatively normal. But if you've had it for a while, then this does sound problematic.
Personally, I'm pretty irregular even though I should be regular by now. But since I never had any spotting or abnormal cramping or anything like that, the doctors weren't too concern (they just thought it was weird). But if you do have spotting and cramping, then this could be a serious sign. You should go see your doctor as soon as you can and tell them about your problem.