wtf is going on

okay i’ve been on the pill for years and ended my period saturday .. this cycle has been weird I always end on friday’s (which it was light then) so I had sex and then full blown had more period saturday .. then it ended (so I thought) started my new pack yesterday as always on time and had sex yesterday and now today i’m spotting? wtf is going on did the sex make me flush out more blood? i’m confused please help