I've Been Dating My Girlfriend For 4 Months And We

I've been dating my girlfriend for 4 months and we have sex regularly. She has been taking birth control for 2 years and has never missed a day. We don't use condoms but I've never gotten fully off inside of her but sometimes I get close and MAYBE a little bit comes out but nothing extreme. She is on her placebo week of her birth control and is on her 3rd day and so far no blood or cramps; nothing. She has been having tender breats lately also. Any chance she can be pregnant? Thank you.