Uncommon bleeding after sex

My period ends, 2 days later we have sex and I bleed during sex. Then 1 day later, sex and then bleed again, 2 days later, bleed again, and yesterday bleed again after sex. I don't every bleed after sex so I am pretty concerned. Does anybody here have any suggestions as to what it may be?

I had an STD check and was clear.

I was pretty lubricated down there during the sex.

It was not rougher than normal and I never bleed.

There was absolutely no pain during the sex.

What could it be??? :(