Wow! very tough situation. I don't know anything about your background but have you ever tried introducing your GF to the idea of D/s and kink?

I mean BDSM is pretty mainstream now and there is lots of advice around about how to bring it up in a relationship. If you have been together 8 years it seems a real shame to have this big secret between you.

Hope things work out for you but life is too short to live a lie.