you used a condom, and unless it broke which he would know of and tell you, that would really be the only way to become pregnant, yeah condoms are only 99% but i do not think you are pregnant. wait 14 days from when you last had sex and if it is positive ou are prgnant, which i dont think you are.
I would suggest getting on Birth Control, and maybe not having sex until you know what can happen and the risks of having sex, so you are not worried other times when you have sex.