period/spotting/BC advice??

okay so i get super paranoid so if someone could give me some insight, that'd be perfect

i'm on birth control, so my periods have been really regular and fairly light, and i only get cramps every few months. but this period that i'm on right now has been really weird.

i spotted for 3-4 days before i really started my period, which has never happened before, and my period blood now is still really dark.

this past month, my boyfriend finished inside me a couple times, and on one of those days, i took my bc about an hour late.

could i possibly be pregnant? what else could be making my period so weird?