Should I be worried?

So something like three weeks ago I got my period. My period is usually very spiratic and by that I mean always late to some degree wether it's a week two weeks or three weeks. When I got it, it was unusually light and instead of having it for seven- eight days like I usually and extremely light compared to the Niagra falls my vagina usually turns into during that time of the month and it only lasted about four days and then it stopped. So the past few days I've been having really bad lower back pain and cramps in my stomach and today I just started bleeding bet heavily and my period according to this app says it still shouldn't be here for another two or three weeks.