The past 2 months I've had irregular periods. Can your cycle change in your 20's?

Hi girls.

okay so the past two months have been insanely weird for me. I have had regular periods since i was 12. I am usually between 28-30 days apart. usually 29 is my typical. The past two months have been 34 and 35. I know its only a few days but that is odd for me. I'm never that late. Also the past two months have had NO physical or emotional PMS symptoms (and to be honest, PMS usually hits me pretty hard). I'm 19, almost 20, I'm not having sex, not on BC, and I am having the same amount of stress as usual, which is just basic school stress. no weight change, no diet change, no new medications, I'm healthy, and I'm active. I just recently (in the past 6 months) have reached the age when i start to feel pain when I ovulate. I'm just kinda worried somethings wrong with me. Does anyone else know what this is? can your cycle change when you reach your twenties?

Thanks :)