Spotting days before period starts

Lisa
I was diagnosed with mild endometriosis after having my daughter.  Been trying for 13 months for a sibling. Had a lap done in January.  I'm still spotting 4 days before my period starts (27-28 days). If I'm not ovulating until day 15 or so, is that enough time? Anyone in this boat? Any insights to help with the spotting would be amazing?