Pregnancy

So I had unprotected sex on Wednesday the 14th at 2:30am and realised the next morning it was my most fertile day and half way through my cycle on the 15th at 3:30pm I took the morning after till! Before the morning after pill I had the worst cramps and still have the stabbing cramps.. Now it's the 18th and still very cramps and feeling a little sick today...I'm just wondering because I was so fertile if the pill may or may not work? And when I should take a test ?