Pre-*** does not contain sperm by itself. If anything, it would be picked up from the last ejaculation. And if you REALLY think about it, here are most of the steps to get pregnant;
1. Sperm must travel through the vagina and penetrate the cervix.(Most dont even make it past the cervix)
2. They have to swim ALL the way across the uterus and to the fallopian tubes, and most sperm don't even make it to the right one. And, again, most of the sperm are dead by this point.
3. They have to 'wait' for the egg to be released, and even the healthiest sperm can only live for 4-5 days in the woman reproductive system.
Pre-*** contains so little sperm that it is virtually IMPOSSIBLE for you to get pregnant from it, regarding the steps above.
But, if you are still concerned, do a test! Hope this helps!