Hello.
You're asking for a guarantee that you're not pregnant--when, in fact, no one can tell you that.
If you're worried, I suggest you buy a home pregnancy kit and test yourself to be sure.
Here are some facts for you:
Even prior to ejaculation, men secrete a fluid which can contain millions of sperm, so even if your partner didn't ejaculate inside you, it's risky to let a very excited penis near your vagina.
In addition, unless you have a perfectly regular "Barbie" period, you can never really tell when you're going to get it--or when you're ovulating. This is why it is recommended that you always use an effective birth control and risk reduction method when being sexual with another person.
For more information, I recommend you check out the Birth Control and Contraception Forum at:
http://www.medhelp.org/forums/Birth-Control-Contraception-/show/382
Best of luck to you. Dr. J