My last period was 03/28/2013. 25 day cycle and last 4 days ...i had sex on 04/10/2013 late night . lately my breast has been sore . can i be pregnant?

Possibly: A person who has a 25 day menstrual interval will be ovulating approximately 12-14 days before the next expected period ( or on cycle day 12 or 13, if one counts the first day of menstrual bleeding as cycle day #1). Therefore, since your intercourse occurred on cycle day 13, and sperm can survive up to 72 hours in the fallopian tubes, it is quite possible that conception could have occurred.