I'm sorry that you seem to be in a predicament. Finding your way to poly is often ugly.
Dishonesty does wreck trust, and makes it hard to have a relationship, open or not. Does that mean you should stop being poly? Not necessarily. It does mean, I think, that you should slow down and think things through. Talk to everyone romantically involved and work things out... which might involve some monogamous couple time to rebuild trust, or it might not.
Here's a thread on seeking poly-supportive counselling: