We've all been there mate... Sounds like she was either a virgin, or had just not had sex for a while... If you had a condom on dont worry about aids or STI's... If your scared still theres no harm gettin checked out, it'll put your mind at rest. It just sounds like she could have been a virgin or out of practise... why not ask her if shes ok? Make it out like your concerned about her and she'll love you even more
im just kiddin with ya, you'll be fine buddy.