Paranoid of getting pregnant ?

I do not want to get pregnant so I refrain from sex but I have this fear that anytime some sexual happens when there is no risk that I am pregnant. I know how pregnancy works it's sperm getting in you during the fertile time or anytime. That means penis in vagina or any other way for sperm to get in you. For example fingering I have a fear that my so touched himself & somehow got the sperm in me. Even if he did not cum. I am 18 & this is sad this is honestly not a troll I'm being 100% honest this is really embarrassing for me to post..