### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
my girlfriend and i was fooling around and we were without cloths and my penis touched her vagina and i think there was some semen on it and 2 days after that she menstruated... which was a day or so late but it was a normal menses according to her and it has ended after 4 days and she feels back aches... what r the chances she is pregnant? pls answer asap i m worries...

### output:

Firstly, chance of becoming pregnant on 2nd or 3rd day of the menses is very, very remote, for practical purpose nil, however you cannot guarantee anything 100%. Regarding pronominal fluid and ejaculation at the external vaginal opening, one has to be careful. From your question, it is clearly evident that there was semen on the vaginal opening suggesting that there was not only ejaculation fluid but also ejaculation. The first part of the ejaculation comes out with a great force. Even when the ejaculation takes place within the vagina, some sperms are known to enter the uterus. So even if you see some semen on the vaginal opening, there is a strong possibility that some part of ejaculate has entered the vagina, which is sufficient for pregnancy. Remember, there are millions of sperms in one ejaculate and to impregnate, only one is sufficient to fertilize the women egg. Furthermore, even pronominal ejaculation also is known to contain few sperms which are known to cause pregnancy. The backache she is getting is probably due to the stress and may be the rigorous activity if at all she had during love making. Pregnancy does not give low backache. I repeat, the chances of becoming pregnant are very very very remote on 2nd or 3rd day of menstruation. The egg is released 14 days before the next expected menses and the life of the sperm is not more than 3 days.