Thanks a lot for the suggestions, good advice. I'll keep working on it.
Certainly it's hurting all of us, even the other girlfriend. I know he does it for her, because it's her who wants a mono relationship, or kind of "pretend" it is. But it's harming her too. Plus, she doesn't show any bad feelings to me, but I know she mustn't be very happy that I'm there.
It's even worse if you look at the timeline of the events,
- Carl breaks up with Paula because he can't stand monogamy any more,
- I start a relationship with Carl knowing we would be poly and find other partners, but there weren't any for the moment, so we were out there openly,
- The ex-girlfriend comes back and I have to step back to the "side" and start to hide while they pretend to be mono, when that is precisely the cause why they broke up in the first place.
Sorry the rant, but sometimes I think I am the only one with a minimum of common sense in this.