Unless there are issues in the pregnancy like bleeding, cervix opening, low lying placenta etc then DTD is generally ok. If you have had a history of m/c then you may feel safer waiting until the 12 week mark.

Orgasms are apparently a great way to tone your uterus and get it ready for birth so it is actually good during pregnancy to get a few training sessions in (you don't need to DTD for that though ). Perhaps the dreams are our bodies way of self-training? It knows what it needs to do.