Trying to be Prg. V had unprotected intercourse in d 3rd week of Fed 2011. Ie. Between 14th Feb to 18th Feb.?

we had unprotected intercourse in the 3rd week of Fed 2011. Ie. Between 14th Feb to 18th Feb. I had got my periods last on 4th feb 2011. My cycle is 28 days, which means it is due on 2nd of March which just after 5 days. I have continuous feeling/sensation in the lower stmch that I would get chums just like always. I normally get such feeling 4-5 days before my period is due. Does that mean I have not Conceived this month ? & I would get my regular period ? :(