Should I be concerned about my irregular period patterns?

I have had my period for about four years now, and after the second year it was completely regular and came at the same time every month. Lately it has become very irregular. At first I would just go 2, 3 or 4 months without getting it. This time I went FIVE months without getting it (don’t worry, I’m a virgin, no chance of pregnancy here) and when i finally got it… it’s lasted TWO WEEKS so far and is still going… and it’s heavy! Is there anything specific I should be concerned about? I already made a doctors appointment but I want to know any possibilities ahead of time.

Thanks in advance for any help!