Why hasn't the bleeding stopped after miscarriage?

If you had faint positive pregnancy test results and the ultrasound did not detect a pregnancy in the uterus, it's possible that the pregnancy did not progress or was very early on. So the bleeding could also be due to hormonal imbalances or other factors. Check with a gynecologist to be rest assured

Periods don't always need to be regular. Irregular periods can occur for various reasons, even after sex and ejaculation. Bleeding three days after sex could be implantation bleeding, stress, hormonal imbalances, or even pregnancy. If you are nervous, you can take a pregnancy test. To help regulate your periods, stay healthy, eat well, and manage stress.

You have a small cut on your vagina after you were intimate. This is no surprise because the skin down there is delicate. It might cause pain, redness, or a bit of bleeding. To speed up the healing process, you can keep the area clean and dry, avoid using scented products, and apply a gentle cream or ointment recommended for cuts. 

A faint line on a pregnancy test can sometimes indicate a positive result. In many pregnancy tests, even a faint line can suggest the presence of the pregnancy hormone hCG. A faint line could mean that you are in the early stages of pregnancy, as hCG levels might not be very high yet. So it's recommended to take another test after a few days to see if the line becomes clearer.