I just don't know how many year of that were fake - probably the last 10
You will never fully know her or anyone else's experience. You only know your own. Whatever feelings you experienced--love, pain, joy, sadness--were real and meaningful. I have to remind myself this sometimes, when I ask questions like, "Was the sex meaningful?" Answer: "It was meaningful to me."
I get you were living a pretense when you neither fully confronted nor let go of the notion she had cheated 10yrs ago. I get that stress/burden may not have helped your health.