Period change...

ok so i’m completely lost on this but I have a dr appointment friday . normally when i’m on my period im always about 2 days late i cramp a week before and have a normal flow well these last 3 months its been different... February i was 4 days late bled for 2 days spotted for three March i was 2 days late bled for 2 days spotted for 3 ... now this month i came on on time bled for 2 days now im barely even spotting or cramping .. i haven’t been stressing about anything either so i know it’s not stress.. & i am NOT on birth control what do you think it could be?