I ‘m trying to understand because I love her

I have been with the same woman for 21 years. It’s the longest, and what I assumed until 2 days ago, most stable and loving relationship I have ever had. I’m 63 years old and she is 74, so I thought that at this point, even though the relationship had really changed over the years, that she was my partner for the rest of my life. She never said or did anything to make me think otherwise.
Except, looking back, I was kind of oblivious. 15 years ago, after 6 years of what I considered (for lack of a better word) a normal, sexual, mutually exclusive relationship and deep friendship, I made a mistake while we were making love. It was a mistake that I have gone over and over in my own head a million times and without going into details that are not appropriate for this forum, she said “you’re hurting me”. I didn’t hear her properly. I thought she said something positive. She said it again louder. I immediately stopped what I was doing (I had done it dozens of times previously but so what, she said stop) and I backed away from her slightly and apologized. Sincerely. The last thing in the world I would ever want to do is hurt her in any way. At the time, we talked for a little while and it seemed to me that she knew that I would never purposely hurt her, that I was horrified that I had and that in the future, I would be 1,000% more aware of her every single nuanced reaction. I know, it’s a little over the top, or maybe it’s not, either way, it wasn’t going to happen again.
Except we never got a chance to find out. From that moment forward, I basically never touched her again, and she never touched me. Over the course of 15 years, she hugged me twice. Once when I was crying uncontrollably after being assaulted, and once when my mother died.
And yet, I thought we were still partners. Every other aspect of our relationship was exactly the same. I was still deeply in love with her, committed to supporting her through all the trials of life, (and she continued to support me), and in my mind, if a person doesn’t want to be touched and they don’t want to talk to me or anyone else about why, then all I can do is continue to be there if she changes her mind or even if she doesn’t.
It’s important to note that I was the first woman she had ever been with. I was also her patient (she’s a NP). I stopped being her patient the moment the relationship started and got a new doctor. I never told anyone who didn’t already know how I met her ( which was 2 people and her 2 adult children). I didn’t want her to get into any trouble because I honestly didn’t think she did anything wrong.
Fast forward to 3 days ago. Wednesday. Our 12 year old dog had died suddenly and unexpectedly on Monday. She had confronted me on Tuesday with the news that she thought that I was “manic” and should be medicated and possibly hospitalized. (I immediately talked to my doctor, told him everything that was happening and he said I was definitely not “manic”. He said I had PTSD. Wednesday, she sat down with me and very calmly and seemingly rationally told me that she was not gay or bisexual and that she NEVER had been. That she didn’t touch me because she didn’t want to “lead me on”. That she was attracted to men, always had been and that was that.
I honestly didn’t know what to say. Literally couldn’t talk. For at least 5 minutes I think my head just spun around while I tried to figure out what the F was happening. If you knew me, and you kind of do by now if you have gotten through this much of my story, you would know that I actually am not a person who is ever at a loss for words. In fact, she constantly accuses me of talking too much and being too honest. (Is that possible? The honest thing?)
At any rate, I ended up getting up and walking away. Because when I finally opened my mouth and started to say something along the lines of “but what about those 6 years etc. ?” She shut me down by talking over top of my first three words. I’m not oblivious to what she needs. I walked away.
On Thursday morning, I informed her that I was going to my friends house to stay for awhile and help her get ready to sell it. The truth. She hugged me six times before I left that afternoon proclaiming that I was important to her, that she loved me as a friend, that she would always take care of me, that she left me the house and $50,000 in her will, on and on, I’m sure you get the picture.
God or Goddess or whatever you choose bless you for reading all this.
I really needed to put all of it out into the universe and see what comes back.
I’m still at the lake. I’m adopting a five month old rescue dog tomorrow. I will have to go back home very soon. To what I don’t know.
I do know that she will never tell anyone about any of this, that she has basically kept our relationship a secret for all this time and that she will NEVER go to a therapist, doctor, anonymous helpline or any other person or place that would require her to be honest about one single thing when it comes to me or anything else that would make her look less than perfectly “normal”.
So incredibly sad. She must be in so much pain. You would never know it. I would. I can feel it. It’s breaking my heart.