could I be pregnant again ?

Okay so I finally got my period and it lasted 4 days the day after it ended my fiancé "finished" inside me.. is it possible to feel pregnant already? I feel like these last few days I've had crazy mood swings a little nauseous and dizzyness lol I'm having anxiety that I'm pregnant again already. Please no rude comments just wondering if anyone got pregnant and just "knew" before a test could actually prove it