What is the intention once the baby is born? You say this is a full-blown triad. Do all three of you intend to share parenting responsibility with the baby? If so, then they definitely need to back off on the sex and help you as much as they can. If not, you'll become resentful, and even more hurt, and that's certainly not a healthy environment for you or the baby.
Some frank conversations with them are needed, I think. If G was really being serious when he mentioned kicking H to the curb, you guys need to have some serious heart-to-hearts about what the plan is. Having a baby is not the time to be having a tumultuous living situation.