I am a male Snake (Sep.20, 1953) and she is Dragon (Oct. 19,1976), will this be a Happy Couple?

will this relationship be happy, and bring peace and harmony?
We met on July 4, 2010. And it has been going from Happy, Perfect Match, to an argumentative connection. Yet we are still together, on and off.
She is now dating a male Rat Yr. (Nov. 13, 1960). We are friend with each other, though I feel like the third wheel. She lives with him, because I am too difficult to be with, says she. Yet I see her most every day in their place .... And she says that she loves and cherishes me (?)
What to do? Five year is long time to figure this out...(?)
Shall I let the Dragon and Rat be together, and walk into the sunset ?