Is my gfI preganant, there was no intercourse and she's late, and stressed to hell, help!!!?

A few days after her last period, she rubbed my penis on her vagina. She claims i released a little but i have no recollection of such a thing. We are 18 and go to college, she's stressed over everything. Ive done research and everything ive looked up comes to a slim chance. Her period shouldve started yesterday she says, but she didnt get it. She hasnt had any symptoms of being pregnant either, and it has been three weeks to a month already. I am scared out of my mind, I dont want to lose her, i love her. Please, dont tell me how stupid i am because i already know. I just need honest answers, please help....