Cramping, no period.

I’ve been cramping really bad. About two weeks ago my period was due and all I did was spot for a day which was weird because my period is always 3-4 days. The last times I had sex was back in November and a day ago. In December I got my period so I doubt it would be a pregnancy but has anyone ever had this happen to them and then found out they were pregnant? The cramping is really bad