Chances of pregnancy?

I wanted to ask about the posibiliy of being pregnant. Well, I had some kind of a sexual activity last week, on Tuesday, but I didn't really had sex. I was like 1-2 days after my ovulation, if my calendar is right. I have very irregular periods,last month came in the ovulation time and it was really light. I am talking about dry humping. To be more specific, by dry humping I mean he only touched me once near de vagina through the panties, then I went to the bathroom, washed and changed them. And when we were fully naked he only touched other parts, but not exactly the vulva, cause I didn't want to risk too much. He didn't before and I don't think he had much of the pre-ejaculation fluid.
My period is supposed to start 3-4 days from now, but I had some bloody, brownish, discharge, sometimes a bit heavier, like red blood , sometimes lighter. I have headached, back pain, sore breast but not constantly and I am also really stressed. I am worried and I don't really know what should I think