I Had I Guess You Could Call It Naked Dry

I had I guess you could call it naked dry humping and some pre-cum came out but that is it, she is scheduled to start her period this week and it turns out she started it this morning. I saw something that is saying it may not be her period but something else. I guess the question is since she started her period is there any way she could be pregnant? Also she is on birth control.