My Period Starts Around In 2 Days On Monday But

My period starts around in 2 days on Monday but I have been bleeding today (Saturday). Could it be implantation bleeding or have I got my periods early ?? as it doesn't feel like my usual period pains or cramps I get ? When Should I take a pregnancy test?

P.S I saw very faint pink/ red/ brown stains at 4 days past ovulation cycle day 16. I have a 28 day cycle.

Thanks.