I did the same thing to and I am so worried:/
You wouldn't know you were pregnant 'overnight'. You said the next day, so that kinda confuses me. But yes you can get pregnant even while using a condomn that's why they say the safest thing to do is to use 2 different methods of protection. But you said the condomn did not break which is great and it's not likely that you became pregnant but even though you saw sperm in the condomn does not mean it didn't leak out because it highly could have. Could there have been another guy you had sex with? Or are you narrowing it down to this guy because you want him to be the father? Not trying to be rude, just help :)