Pregnancy chances from precum

My girlfriend and I were having sex and we decided after we were done but i was still hard that we would see how it felt to be inside without a condom. This was near a month ago and were terrified that she may be pregnant. She hasnt really shown any signs of being pregnant but her period is coming up soon and she has been showing signs of that, but some of the signs of a period are the same as pregnancy, were scared shitless....any advice or reassuring words? I don't know if I did or not but I don't think I pre-came but its supposedly not feelable. Keep in mind shes going to be getting birthcontrol tomorrow and we will never not use a condom again.