I Had Sex With My Boyfriend Yesterday, And When He

I had sex with my boyfriend yesterday, and when he pulled out, the condom was still half inside me, but I don't think any of it got into my vagina because i took the condom out and his cum was still inside of it. I'm just stressed there might've been a slip anywhere, I don't know what to do. Don't want to take the plan B because it makes me gain weight. What do I do?