I Got My Birth Control Shot A Week Late My

I got my birth control shot a week late my doctor could not schedule me in i have not had any period spotting nothing this is not the first time i was late getting it i had a urine test done because i was late it came back that my gravity was off? Me and my boyfriend had sex two days before this shot and now all the sudden i have heavy bleeding and feels like i am pregnant i have three children so i know what i feel like could this be possible? Could that be why i am bleeding?