Pregnant?

Okay so on march 28th i had a one night stand... I was drunk... And he swears he pulled out... But on the 5th i was supposed to get my period ... Instead i had very light spotting for like 2 days then ot stopped for one and then i spotted again for 2 days... ... I dont think that was my period even though it satarted within the time frame of when i was supposed to get my period... My cycle is a 14 day cycle on the dot and very predictable. .. And im always really heavy... Is this a freak light period or possible pregnancy ? My periods have never been this light...