What are the chances of my girlfriend getting pregnant if i used a condom every time we've had ?

me and my girlfriend recently started having . she was not a virgin. we recently had on June 17th and i used a condom. she was supposed to get her period around the 21st. we did it again on June 25th and i also wore a condom. on the 27th she said her feel heavy. now it is the 29th and she still hasnt gotten her period. what are the chances that she is pregnant?