Sir I'm 21 Years Old Guy.My Gf Is 20.we Had

Sir I'm 21 years old guy.My gf is 20.we had made a mistake on 10th of august.we didn't had sex.i rubbed my penis on her vagina.my little sperm came out on her stomach but didn't touch her vagina.i didn't penetrate my penis on her vagina.her hymen is not broken.its 13of august she hadn't taken any pills.is there any chance of pregnancy.please help us we r really worried.what we should do.her last period came on 20or 21 St of july