My period is acting weird

Soooooo I know that I can get pregnant 2 years ago I had an abortion and I’ve been trying ever since then because I felt so guilty and bad for killing my baby so I’ve been trying since then. My period before the baby was perfect it came on time every time never later and last for the same amount of days but NOW! Since the abortion I’ve been having hell with my period! Lasting from 3 to 7 days sometimes I’ll have a period in the same month. Every time I’m late I think I’m pregnant but I’m not! Any one have any answers as to why my period is like this