Ok im sure this post has happened before but im new so yeah. Ok well from waht ive read and stuff in other posts for a girl its hurts the 1st time well if it hurts like how do you know when to stop and does anything happen for her and that sort of thing.
If she looks like shes in pain?
Its a fair but a bit rediculous a question. You'll know at the time if shes in pain or not, and she aint gonna let you fuck her if its hurting her anyhow. Takes 2 to tango y'know :P
She might say to slow down or go easer or she'll tell you to stop if she's hurting.
Sex the first time is often not a great experience for either side, but it gets better.
I remember your girlfriend doesn't say much, so you'll have to be careful and gentle with her. However, there's usually not too much pain. Pain (and a bit of blood) can come from tearing the hymen, but it's common now for that to have already happened from using tampons, or some other reason. If it does happen, it should heal quite quickly.