What Are The Chance Of Pregnancy If Pre-ejaculatory Fluid Enters Vagina?

I am 23 years old. My boy friend and I had physical proximity last night which was not actually sex but his penis was touching my vagina. He is sure he didnt ejaculate but some precum might be there. Can I get pregnant? Should I take i-pill? What are the side effects if I take one?thanks a lot in advance.