Abnormal Spotting-help!

This is a long post but can anyway relate? Or know what is going on? I have 1 son who is now 2.5 years old. Shortly after I got my period back from childbirth I have been spotting at random times throughout the month. I had a d&c; in July which removed a polyp, hoping that would stop the issue. I got pregnant shortly after that and had a miscarriage in October. I am still spotting! Sometimes it’s sporadic during my ovulation week but usually always the week prior to my period. It is generally a maroon color but this month I had some bright red. I started fertility pre-screening and my X-ray, ultrasound and bloodwork all came back fine. No one has an actual explanation for me! I’m really just tired of surprise bloody visits and not knowing what’s going on. Also just annoyed to still not be pregnant but at this point I just don’t know if something is wrong? Why is this happening and what can be done to stop it.