What Causes Dark Spotting Immediately After Sexual Intercourse?

I had a misscaraige on Feb. 18th and passed it on Feb. 24th, bleeding stopped around 3-4 days ago, so today I had intercourse and had some dark spotting immediately afterwards. It wasn t like the bleeding I had during the miscarriage that was bright. Not sure if I should be worried it s and infection or not. I have no pain, and no fever, but have had a very slight amount of discharge.