PennyB, welcome

I'm so sorry for what you're going through but I'm glad you're here. The loneliness is so hard, isn't it? Most of us can relate to not being able to talk to family or friends about this. There's so much they don't/can't understand.
When he is stable, do you feel connected?
It's not ok that you feel like a dumping zone. There's a balance to listening, validating, and if necessary, protecting yourself with boundaries. This board is a great, safe place to vent and hear from others. We can share our experiences and what we've learned and help you come up with practical ways to improve communication with your fiance.
Have you set a date for the wedding?
pj