I am fifteen, almost sixteen years old.

Me and my boyfriend were "dry humping", me in my underwear, him in nothing. He said there was no precum or anything, but I knew that my underwear could have been that wet from just me. I couldn't go home for another few hours, so I cleaned myself as well as I could, and put toilet paper between my vagina and underwear for the time being. (about 20 minutes after the dry humping.) after i got home about for hours later, I got right in the shower and changed my clothes. This happened about four days ago. Could I be pregnant? Can you get pregnant from precum? I am supposed to be getting my period in a few days, and I am starting to get cramps late yesterday, and today. Could I stress too much, and miss my period?  HELP.