What Causes Mucous Filled Clear Vaginal Discharge With Streaks Of Blood?

I am 4.5 months postpartum, exclusively breast feeding. I ve had weird discharge the past 5 days. First clear, mucusy with blood streaks, then really dark brown, enough to use tampons. Then the past 2 days are stringy very light brown/grey when I wipe. Could this be my first pp period?