I Hate My Period

I've been tracking my cycle with an app and it's always been spot on until last month.
It was just a day off, but when it happened my period looked all weird and kind of grainy, but I bled for the normal amount of days.
Well this month, I'm 4 days late now, and have been having cramps and I feel like it's going to happen soon, but I'm a bit thrown off by the weirdness...
If anyone has any info to share it would be nice.