The cervix becomes very vascular and engorged during pregnancy, as long ad you aren't having any cramping and it's not copious amounts of blood and there are no clots, its perfectly normal to bleed a little after sex.
Im 24 weeks also. I went to the ER about 2 weeks ago due to some blessing (different reason) and before they knew why I was bleeding they told me that we have extra blood so any little thing makes us bleed. She than said it was fine as long as no pain and you don't bleed to the point where you fill up a pad! Good luck (:
I don't think its anything to worry about. Sometimes when you have sex it does make you bleed after. As long as it isn't gushing or a large amount I wouldn't worry
Dark blood or light blood?