What does it look like color wise? How long does it last?

My husband and I have been TTC for 3 years and am currently seeking a fertility doctor. I have my thyroid in check with meds, I took an ovulation kit last month and had sex 3 days in a row when it showed I was ovulating. My doc even did blood test to show I actually ovulated for that month and I did. I have glow and pink pad, glow says I should be getting my period on 8, 9, 10, but pink pad says like after the 12th. I keep spotting not enough to use a tampon but enough that I worry and wear a panty liner. ( nothing ends up on it) I've had dark red blood and brown blood but its been going for 3 days now. Is this implantation bleeding or am I just getting my hopes up. Next step is <a href="https://glowing.com/glow-fertility-program">IUI</a> so I want this to be it so bad!!