I Had Unprotected Sex With My Girlfriend. She's Been On

I had unprotected sex with my girlfriend. She's been on the pill for a year but two weeks after we had sex she switched to the shot. She said she had her period when she switched to the shot, but switching birth control so close to unprotected sex has me worried. Is there any chance she's pregnant? She says she doesn't feel pregnant and it's been a little over 6 weeks now.