Is It Good To Have Light Bleeding Before Menses?

Hi Doctor.. I am TTC not ver long just two months.. but find something strange ..couple of days before my period is due I see very light bleeding .. i mean very light.. it continues for a 2-3 days and then get a very heavy period,, this happened a month back.. again see similar coming as my period is due on 23rd and since 19th I m seeing a spot of blood sometimes in the tissue.. is this normal .. this has never happened earlier