Spotting with thick discharge

Sorry for such TMI but I dont know if this is implantation or what. Heres the deal. I started my period on March 5th, it ended on the 9th. My husband and I had plenty of intercourse on the 16, 17 and 18-but use the pull out method (I know, I know) and now on the 19th and today (20th) I am spotting to where I need a liner and its thick and brown with some pink. What the heck is going on? AM I just ovulating? I dont typically spot or bleed with ovulation. You would think I would know with having 4 pregnancies and being 30 but this is unusual for me. Can anyone give me some insight? Thanks.