Advice please

I was on the birth control (pills) for a long time and have been taking one always before i go out for work. Last Saturday was my last day of taking the pill and that day i had a sex with a guy but he didn't pull out and did it inside.... I didn't take more pills since then as i finished my 21th on Saturday morning and not have not bled yet. I am feeling headaches and nausea and a bit of pinch in my stomach (not feelings) which are not usual symptoms for me. I think the possibility will be really low but do you think this is something to really worry....