Am I overreacting?

Recently lost my virginity on Saturday. I told the guy I was ovulating and to be very careful. He used a condom and did not finish in me. I don't think I came into contact with any pre-come but I don't know. The condom as far as I know did not rip or tear or break (it was the Trojan Enz spermicidal kind). But I've heard that you can get pregnant off of pre-come? Is it possible to slip out of condoms? I'm not on any kind of birth control. He's not a virgin and said he was very careful. I'm still within the 72 window for plan b but I seriously don't want to consider it. I guess anything can happen, but I'm just stressing the 'what-ifs'. Any advice? We are both in our mid twenties and are just trying to be as safe as possible.