HI My Periods Are 11 Days Due. Supposed To Get

HI my periods are 11 days due. supposed to get on 4/11/2015. Last period was on 3/10/2015 got spotting on 24/10/2015 thought my period was due but till today no period. Slight cramping are there. Me and my bf did not have any intercourse but just touching and he did his ejaculation himself. As per HPT yesterday it was negative. What could the reason be?