I hate to say it, but yes, you could possibly be pregnant. The pre cum does contain live sperm. It only takes one sperm to make it's way into your vaginal canal to become pregnant, and if you are rubbing at all, that sperm could be forced inside of you without your knowledge. Even during clean up after orgasm, you can wipe the semen inside with a towel by accident. The sperm can live inside for up to three days, so there is a window of opportunity there, even if you didn't ovulate prior to your contact with your boyfreind. It is very rare, but not impossible at all. I would have a blood test done right away to confirm it.
My husband and I work with teens & young adults. Unfortunately this is more common than you think. Even if you ar enot pregnant, you might want to reconsider how vulnerable you make yourself to another person when you engage in any kind of sexual activity like this. Disease is something that can occur without penetration too. Almost all sexually transmitted diseases (including herpes, which 1 of 5 active people have!) can be passed along this way. All it takes in some cases is skin contact, or contact with any bodily fluid.
I hope this helps. Please see a doctor right away, and treat yourself well, whether you are pregnant or not. You deserve it, and you may not get a second chance to gaurd your health and future again.