Cycle 4 TTC

I have a very regular period 28 days every month since I started. This month I had pink spotting on 5dpo.... Then again spotting pale pink/brown cd 9-12 it comes and goes. Tested with a frer yesterday CD11 negative in the afternoon. I'm just curious what's this spotting about does it take this long for periods to regulate after stopping BCP?? The first 3 months off the pill was normal now this strange spotting! I'm testing again friday(AF due) I just have never had this before any insite is welcome.