Do you belive my girlfreind is pregnant?

Patient: We had unprotected sex last thursday night”The 11th” but I am almost positive I didn’t Ejaculate inside of her as I pulled out moments before when I felt the pressure of cumming.She woke up this wednesday”The 17th” morning saying her breast were tender. We’ve had a absence of sex for the last month and a half before this session of having sex because she was out of town. I’ve read around about hormone imbalances sometimes being the reason for tender breast after having sex when not doing it for awhile. She seems to be on a normal 28 day cycle so with her period beginning the 5-6th and ending the 10th making her time of ovulation around the 18th. What is the likely hood of her being pregnant? I know not using a condom is like playing russian roulette giving you an average chance of 35% pregnancy.I had not had any previous sexual encounters the day and had definitely urinated since the last time I had ejeculated so my “Pre-Cum” should of not contained sperm.