late period!!

Hi, I had sex on the 22nd of January and we did do it with a condom but he stayed over at mine and throughout the middle of the night we ended up doing it spontaneously without any protection. However I was on the pill so I didn't think I was being completely stupid. Since then I haven't had my period even though they are irregular so I don't know when it could come but I'm worried about pregnancy because I seem to be having all pregnancy symptoms apart from throwing up. Someone please help? What should I do. X