Hopless after 23 years

My wife of 23 years denies me sex every time I try. I put my hand on her and she says she is feeling attacked. I try to do everything she asks and needs to make her happy and do less thinking that was the problem. But time and time again she denies me sex. I’m so frustrated. Everything was fine six months ago and then she just started making excuses for not having sex. I don’t want to waste all that we have shared but I feel like stepping out and giving up. We have talked about it over and over again for last six months atleast 3 times a week and she always says she doesn’t know why she just doesn’t feel attracted to me anymore like that. I meantioned having a open relationship and she said no. Lost and confused.