Andrea,
A support group can be of value certainly. I've found that interacting with other TGs is helpful in putting things into proper perspective. The goal should be to find a way to achieve peace of mind with the least amount of collateral damage. Others can often help you see possibilities that you haven't considered. I understand that a support group doesn't exist in your locale. That's a shame.
This forum is also a source of support. If you're reluctant to be too 'public' is discussing issues, realize that there are lots of private exchanges among members that play a big part in finding needed support and comfort. It only takes the courage to reach out to someone who you believe can relate to your particular circumstances.
When I hear accounts of relationship problems arising from TG issues, I realize how differently much of the world views this medical condition. If one announced that he's been diagnosed with cancer, diabetes, or Alzheimer's, I doubt that many spouses would respond, "Well, if you insist on seeking treatment for your problem, I'm not sure our marriage can continue." Why is it so prevalent with trans gender identity? It doesn't have to be that way.
It's terribly important for a spouse to understand the nature of what you have been coping with as a TG. She needs to understand that gender identity is inborn, not forced on you, and not a lifestyle choice. She needs to understand that the dysphoria only intensifies with the passage of time. She needs to understand that there is no cure, only treatment to reduce the GD.
I strongly recommend that you read a book by Jennifer Boylan entitled
She's Not There. It's the true story about a straight man who finally comes out to his wife about his long-suppressed transgender identity, and the way they each learn to deal with the crisis and stay together in a loving relationship. I'm betting that you will relate to their struggles as you are navigating a similar path in your own relationship.
Clara