What Causes Vaginal Bleeding After Taking Morning After Pill?

About a week ago I went to the doctor to get the contraceptive pill however he told me I could not start it until the first day of my next period. However, when I had sex the condom split and I took a morning after pill. Now I have bleeding and cramp which is a side effect of the pill (which I experienced and it went but now it is more blood and more cramp how it feels when I normally start) but I cannot tell if it is my next period starting or a side effect.... So I do not know if I should take my contraceptive pill