Could my girlfriend be pregnant?

My girlfriend and I are both virgins, and we decided not to do anything until she's 18, but she came over to my house and we started fooling around. Next thing you know were both naked, but were not going to have sex. I made contact with the outside of her vagina for about two seconds with my penis (no penetration at all, just at the mouth of it) and i believe i had pre-*** on my penis. however i had not ejaculated in the past 24 hours, and even if i had, i had urinated 30 minutes before. that was two months ago, and she's had her regular period twice since then, however on her last period, she had cramps so bad that she began to cry. is pregnancy possible?