Go get "plan b", you can take it up to 3 days after unprotected sex.It could take that long for the sperm to reach your egg and plan b stops the sperm. You could be pregnant even if he didnt ejaculate in you. "pre-***" ejaculation has semen in it and all men pre-*** wether they know it or not.
If you were at the right point in your cycle, you have a chance of having gotten pregnant from this encounter. If your period is due tomorrow, your chances are very slim. If it is mid-cycle (about halfway between your periods), then your chances are higher.
When a couple is trying to conceive, they are told that they have about a 25% chance of getting pregnant in a given month. That is an average; the younger you are the better your chances.
Given your situation, unless your time of the month strongly suggests you would not get pregnant from this encounter, I would consider taking Plan B today. It is available over the counter at the pharmacy, and I've heard that if you take it within 72 hours after the unprotected sex, it will work as expected and you won't get pregnant. Apparently taking it within the first 48 hours is the most effective.
of course there is 85% of chances that you can be pregnant .