I see it's only been 2 months since "She" entered the scene. And the ED arrived full time for you then...
Do you mean it happens with Him when She's not even in your home? He can't fuck you at all any more? I assume you and He do it when She's not there? Do you and She do it without Him? And He and She alone?
Threesomes, emotionally and physically, usually are very challenging in many ways. And men here do sometimes experience not being able to stay hard with a new lover. In this case, he's hard for her, but not for you. I imagine once the newness wears off things could change.
OTOH your new female lover using a vibe on you, or her mouth or hands, could be a nice new experience while your h's penis adjusts to new demands.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
There's no lying in polyamory!
I'm a 58 year old woman with 2 partners:
miss pixi, my live-in gf, 36 (together since Jan '09)
Ginger, bf, 61, married, lives nearby (together since Jan '12)