Is my girlfriend pregnant?

Ok, two days ago I had my girl friend over we did touch each other (i rubbed her through her pants and she stroked me for a few seconds right befor i took her home), when she went home a few hours later (two hours later) she played with her self, i was worried if she had some of my pre *** on her hand but she told me she didnt (I asked this twice) (and in the car earlier i have tried to wiped her hands off with my hand), now today she worried she might be pregnant cause she says she has a stomach ache, also she hasnt had her period this month yet. Also she isn't late, she says she gets her periods at random times each month, bur her last one was at the very end of April, so I would ume she'll get it at the end of this month. But Is she pregnant? cause she's freaking out and that's making me freak out....