Hello and welcome to HCM. I would be pleased to help you. The most likely possibility is bleeding from the cervix
. The cervix can sometimes be "friable" or prone to bleeding. This is not uncommon, and might even vary based on where you are in your cycle.
Regardless, you are right, this might be a sign of pregnancy
. Especially given that you are continuing to bleed even well beyond the intercourse. Here is what I would recommend:
1. Do a pregnancy test now
2. Repeat the test in 1 and 2 weeks from now
3. If these all remain negative, then you are not pregnant
This is most likely normal and related to the sexual activity itself. But don't ignore your instincts and go get a pregnancy test. I hope this helps and good luck!