I really need some help, I’m confused /:

So me and my boyfriend has unprotected sex ( Aug. 29th night ) and he did come in me, the next day we went to get a plan B and I took it. My period only lasted about 3 days and that’s very rare, one of the first time to be that short.( Aug. 24th -26th) now forward to today, I’ve been feeling very weird around my stomach chest area, like if I’m nervous and like if my blood pressure went down. I noticed last night that I had started bleeding again, and today is has been none stop, like a medium spotting. Could this be because of the plan B? Or what could it be ?