Sperm count and Marijuana

Diamond

Me and my partner use the withdrawal method but just for one time he recently did not. I didn't think nothing of it because he smokes so much weed, I know his sperm wouldn't know where to go. 3 weeks later I've had my period and everything is normal but for the last 3 days I have been very nauseous with no appetite. I know you can't tell this early if your pregnant or not but what should I do?