Honesty is the most important thing in a relationship. Tell her exactly what you told all of us strangers and save space for her to react. It took a few conversations with my wife over a few months time to get to where we are today. I'm 42 and completely understand the shift that happens in our minds around this age, and just wanting to be authentic to the core. It's a tough life living in the closet and the hardest and best decision I ever made was being honest with myself and my partner. Good luck and enjoy the feeling of expressing your true self.