I suppose you can always try our Dating & Friendships subforum
for starters. It sounds like you might have some rough patches on the road ahead as you figure out your boundaries and what you can live with. S has set a rule, no relationships with other males, and you'll have to decide how you feel about that.
Perhaps just writing out your feelings (such as on Polyamory.com) will be helpful. Let us know what we can do to help.