Help! Dom/sub!

We have a pretty healthy sex life but after 9 years we need some excitement. He said he is always the dominant one and would like for me to be more dominant and more dirty talk. I’m a super shy person and also very pregnant. Any suggestions on how to do this without feeling awkward? We do occasionally bring up the mmf fantasy during sex and ffm. This is just a fantasy though we don’t want to go that far irl. He has security issues because he isn’t that “big” so bringing in another through talk is how he thinks I can be taken care of correctly. But he’s great in bed. We are also into light bdsm. Idk from a female perspective how to go about it. He says he wants me to tell him and show him that he is what I want.