In december 2014, i had cramps for a week and few days after i was spotting. on the 25th of december my menstrual cycle came and lasted about a week, ?

Irregularity: Are you on hormonal birth control at all? This can commonly cause random spotting/cramping. If not, I wouldn't get terribly concerned at this point as you did end up having your normal menstrual period without delay. Sometimes the hormones in our bodies get out of whack and cause irregular spotting and cramps at times which is "normal". In the future, if missing a period, check a pregnancy test.