Is it possible that my girlfriend is pregnant?

okay. Today is August 1st. Last tuesday, July 24, my girlfriend and I were messing around and I cmed..cleaned it up..but did not urinate. later that day, we were messin around again and after about 30 mins my dck was really close to her Vagina. We have been going out 9 months and are both virgins and want to wait a little longer to have sex, but at the time, we were both so horny, we thought we would try to just stick it in for a second. to see how it felt. I regret that so much right now. It was only in about an inch and a half. and I pulled it right out because it hurt her. I know I didn’t Cum in her, but it is possible there was a little drop of precm on the end of my Dick. Last month she get her period the 25th..it is now the 1st. She will be one week late tomorrow.. But the time befor the 25th it was the 20th, and the time befor that, it was the 29th..So she is often all over.. I just need to know.if I should really worry about this..or try to relax..I know she is stressed and I think that it why she is late. but since..it would only be a drop of precum and only in about an inch and a half..I dont know what kind of chances there are of her being pregnant. It was also near the end of her cycle. so I dont know if that has anything to do with it. neither of us are ready to be taking this risk, but if anyone can give me some information on how likly it is that she is pregnant it would be appreciated..thanks