how high is the chance that my girlfriend is pregnant?

hi, I and my girlfriend had unprotected sex and my concern is how high is the chance that she is pregnant? We had sex during june 8 during that time she was not feeling that perfect and might be coming up with something(cause she was a little hot) but still we had sex, during sex it was feeling greet so i had to pull out my thing and when i pulled it out i came the moment it was out and not sure if some pre-cum got in.Being concerned about the pre-cum, I told  my GF to wash hers so she did with some soap and water. After that "the day after" she was feeling some cramping cause she was expecting her period around those times although she is irregular so her period is not that accurate to predict. During 9,10 & 11 she was feeling the cramps and eventually on 12 it arrive but then ended in 13. She told me that it was her shortest period usually it last 3-5days but that one was shorter than usual, on 12 it was "kind of heavy" then on 13 "it was light". during june 9-13 she was not at her peak health as expected, she had flu,sorethroat,head aches and in addition the cramping cause of her cycle. Another factor, june 10 was her first day of work as a nurse in training so she was expose to a new kind of stress. My main concern is how high is the chance that she is pregnant or is she pregnant? Please help because I'm feeling a bit paranoid and I'm not yet financially fit to be a father. Thank you very much.