Welcome to our forum.
Some links that might help you locate a poly-friendly counselor:
In what way are your feelings deteriorating? What kinds of emotions are you experiencing? What kind of thoughts are going through your mind?
Mono/poly relationships have been known to work, but the monogamous partner often has to experience a mourning period for the monogamous dream he/she had that is now coming to and end.
If she is caught up in NRE (New Relationship Energy), she may be neglecting you without realizing it. Ask for the attention and reassurance you need.
Have a look around at our various threads, and post any questions you may have.