Me and my girlfriend were involved in some sexual activity on the eighth day of her period.Her vagina was too dry and we just did mutual masturbation. I took out condom.While taking out condom,one drop of semen fell to my pubic hair and I wiped that too with a dry cloth. After around 10 minutes,I used another condom. She rubbed her outer part of her vagina, upto clitoris on my pubic hair (where my semen has dropped) for around 30 times ,where I was doubtful that some dry semen could be there.After 3 days, on the thirteenth day of period,her vagina is normal and not dry but she has few drops of blood on her underwear.She has never got such spotting earlier ever in such fertile time of 13th day. She is 25 now. She has no pain but slight lower abdomen discomfort.She has no sore or hard nipple now. Could this be sign of pregnancy ? how much chance is there to have pregnancy in such cases ?