Whats the possibility of her getting pregnant?

Hi there!

Had an unprotected sex with gf on 7 January using pull out method. Had cummed 4 hours before the unprotected sex and did clear out the semen with urination. Her last period was on 21 Dec - 25 Dec 2012.

Tested HPT on 20th and 21st January and came out negative. On the 21st January she had her period that's heavy lasted till 25 January. On the 29th Jan, 5th Feb and 9th Feb tested HPT again, and all came out negative. The last HPT was yesterday and came out negative as well. Overall was 7 HPT with 2 CLEARBLUE DIGITAL used, and all turned out to be negative. And not to forget, did all with the morning test.

Whats the possibility of her getting pregnant? Thanks!