Could I be pregnant?

Me and my partner had an accident with a condom on day 9 of my cycle, I took the morning after pill late afternoon on day 10, it's not day 43 so looks like I've completely missed my period, could I be pregnant or could it have been the morning after pill that has made me miss a period, I did have some dark coloured discharge at about day 28. I also tool a pregnancy test on day 30 and it came back negative. Should I take another one?