Is it possible to still get pregnant after taking the morning afterpill?

I dont mean, will it make me infertile etc, i was wondering if even though i took the morning afterpill 24 hours after the condom split. Could i still be pregnant? what are the cnaces? the reson i'm asking is, although they warn that your period could be late and everything could be a little wonky after taking it, my periods not come but i have had cramps for a good week and i've been feeling a little off colour!