How much of a possiblity is she pregnant?!?

Ok so my gf and i, shes 21 and im 23 so lets not get this your too young to have BS, we had PROTECTED , i did *** inside the condom inside her, it didnt break at all either, right in the middle of the month and she usually gets her . at the beginning of the month and shes really worried about being pregnant and its really starting to get me worried too. we used condoms, we were very careful of what was touching where and made sure we didnt have any mistaken contact. just curious to if shes just stressing out and causing her body to go into overdrive and getting it late or really could be pregnant.