Is she pregnant or not? thanks?

i went to my girlfriends house. we are 13. we started kissing. she pulled my boxers on. but the whole time she had a thong on. it never came off. we were close and we both felt something wet, but i dont think it was me. i didnt see any wetness on my penis or on her. could it have been her? should i be worrying, the next day at school she felt like throwing up with a stomach ache. this is a pregnancy sign, but is it too fast? what should i do? im scared,