Period or implantation?

Hi,

I came off pill mid January and TTC. Had 3 periods since. Now about 32/33 day cycle. In March it lasted about 3.5 days but this month I got spotting (pink) and light cramping on left side. Hoping it was implantation but then next 2 days normal bleeding (red). Today only had light brown spotting which means bleeding was really only 2 days. I took pregnancy test after what I thought was implantation bleeding and was negative. Is it okay my period was only 2 days and is it definitely period if red blood? Or should I re test?

Thanks all!