Can sex trigger your period?

Recently I had sex with a guy after a year and a half of celibacy. He’s bigger than other guys I’ve had sex with and the day after we had sex as well as for days afterwards I’ve been moderately/heavily bleeding as well as experiencing cramps. I’m not supposed to get my period for another month and a half to two months (I’m on birth control and skip the placebo weeks as advised by my gynecologist so I only get my period every three months very consistently) so I’m alarmed as to this bleeding and possible period. I am pretty sure it’s my period as the flow is too heavy to be just spotting and there is also large clotting as well. I’ve tried to do other research and from what I’ve ascertained sex shouldn’t trigger your period unless it’s a couple days from starting anyways. I called my gynecologist to schedule an appointment but in the meantime I’ve been really anxious about it. Should I be concerned?