I’m scared and I just don’t get it ...

Me and my boyfriend been having sex for 1 year and of course we would never use condom or anything to prevent me of getting me pregnant but , I just think it’s weird that every time we have sex and he ALWAYS sperms on me I can never be pregnant .. why ? If he always sperms on me I don’t why I haven’t gotten pregnant please help me .. I’m really scared that maybe I can’t have kids or something I’m just scared ..