Sex before period, have your period before your body realises you are

Me and my boyfriend had sex two days before my period , he cummed inside of me. And I did have my period but it was unusual brown , lighter than usual , but still heavy bits. And now after my period I'm having really odd twingy cramps and tiniest pain boobs on the side. And they're like the same as PMS but like not. So could I be pregnant after my period seeing as it was so close to it. And that I still shred my uterus lining whilst fertilisation was happening so my body didn't realise ?