Honestly, the chances of her being pregnant from that are infinitely small, I wouldn't worry about it. Unless she has a REALLY irregular period, she's 99% not ovulating anyway... plus if you pulled out, there is a VERY small quantity of sperm in precum - its theoretically possible, but would be absolutely shocking statistically. Her feeling weird is probably psychological, she may also have gotten bruised or chafed or something if there wasn't enough lube or you didn't know what you were doing (no offence, no one knows what they're doing the first time, practice makes perfect!). Buy some rubbers, keep some with you all the time, just to be safe. If you're going to be sleeping with her regularly, double your protection - have her go on the pill too. Whatever you do, DON'T USE TWO CONDOMS AT ONCE - the two rubbing against each other are MUCH more likely to break than if you just use one.