You can also go to Planned Parenthood and get the Plan B Emergency Contraceptive for free! Good luck.
If you don't want to be pregnant you can go to your pharmacy and ask for Plan B. That way, if your egg does get fertilized it won't be able to attach to your uterine lining, and will be passed when you have a period. It doesn't prevent fertilization, but it does prevent a fertilized egg from implanting.
I would think you would notice that he didn't "finish" without him having to tell you - a little surprising.
Are you sure he didn't ejaculate inside of you? You can still get pregnant with precum remember. Your periods and ovulation time obviously have a lot to do with your chances as well. The decision is yours when you consider all the factors.