Can anemia shorten my periods? This month I had my period one day early which lasted a day (bled just once), my hb came out to be 6.3

No. I hope someone is working up your very low hb level which is not normal needs an extensive workup and a low hb is associated with heavy , not light bleeding, there can be many causes for a low hb, u need to see your regular doc, a gyn and maybe a hematologist.