Implantation bleeding or an early period?!

Hello! Can anyone help me? Im trying for a baby with my husband, I started my last period on 25th December. I done ovulation tests which showed I was ovulating on 9th January, I had sex on the 8th and 9th. My usual cycle is a month but yesterday I started bleeding rather heavily, over a week before my period is due. This is not spotting. Last night and today has been a steady flow of red blood. This seems to have eased off now. Does anyone know if this could be implantation bleeding or more likely to be an early period? Its uncharacteristic for my periods to be early but i didnt think implantation bleeding would be so heavy so Im confused! 

Any advice or past experiences are very welcome!!!