pregnant?

Okay so recently me and my boyfriend had sex and we used a Condom but it came off half way through without us realising so we put another one on after it came off, I got my period 2 days after but it was very light and only went for around 3 days when it's usually very heavy and goes for 5-7 days, it's been around 2 weeks now and I've been feeling quite nauseous and been needing to go to the toilet quite a lot, I'm not sure if these symptoms are just me being paranoid and worrying about it but I'm not quite sure what to do