Welcome!
I think everyone here would agree that your relationship with Christ is far more important than whether or not you live poly. With that in mind I would encourage you to return to a local church if you can. You will not find one that is poly friendly, but that is ok. Just keep that to yourself there and otherwise enjoy the fellowship, encouragement and Bible study. The pot-lucks alone make it all worth your while.
The chruch is made of of people and therefore it is flawed, but still useful for encouragement and fellowship. Further I would exhort you to grow and mature as a Christian and become the type of person that looks for others who need to be encouraged.
Remember: it is not an either / or proposition: you can still be involved here and go to the retreats and maybe God has a plural marriage in your future.
If there is anything I can do to further your Christian journey please let me know. I am sure anyone else here would be glad to help you as well.