I had the best night of my life and the realisation is destroying me

My partner (40F) and I (40M) have been together for nearly 20 years and married for 15. Three kids. I have intense feelings of love and desire for her. We are a great team and have a respectful relationship. However, we have always had a lacklustre sex life - before kids it was better but not great. I am HL and she is LL receptive. We didn't have sex on our honeymoon and I don't think I have ever gotten over that. I could probably guess an average of sex 6 times a year for our marriage including years where we had no sex and years where we were conceiving. I have never, ever pressured her for sex and respected her wishes. A few times now I can tell she has allowed sex to happen but wanted it over quickly.

I let it go a lot during our parenting years. She breast fed our three children who were all born 4 years apart. Growing, birthing and nursing three children takes its toll on a woman and I have deep admiration for her as a result. I could see how it affected her interest in intimacy and accepted that as a fact of life.

I would add that I did not enjoy the conceiving of the children. It felt so performative and dutiful.

Fast forward to us hitting 40. Our youngest is moving out of toddlerhood. And my partner's hormones are rebalancing from motherhood and entering peri-menopause. There is a shift in her moods and feelings. Intense positive energy followed by intense doom and gloom. I want to be there for it and for her.

But - and I feel like this is something I can't really say, without sounding like a total asshole - the feeling on my end is that I am desired once a month. At ovulation time. There are two days a month where I am the best thing in her life. I get nice comments, messages, flirty behaviour. And yes, I can now expect intimacy on those days. Which is progress in the grand scheme of things. Outside of those two days, I am an irritant to her, I cant say anything right, I am not physically attractive to her and so I just put my head down, work and parent. I almost zone out of it.

A few weeks ago, I had to travel away for work purposes. I was away for the few days that overlapped with her ovulation window. We missed each other. It was good to get some space. It also meant that there was this distance and anticipation of my returning home to her and vice versa. On my way home I got suggestive messages, sex was on the menu tonight and I couldn't get home quck enough. As soon as the kids were in bed, that was it, BAM, we were at each other like teenagers again.

I had the best night of my life. We made love in a way that we have never really done before. It was passionate and loving and satisfying.

But it was like breaking a seal. I immediately wanted to repeat the event. I playfully begged her for us to do this again tomorrow. I gave her affection all day long. Then life got in the way. Parenting and anxiety. She got stressed, and the evening came round, and it was back to square one. Tired and just wants to chill. The mood completely shifted and we were unable to make a repeat of it. And now it will be another month before anything like that is going to happen again.

And it kills me. Sex with my wife is the happiest I can be. One one hand, there is no pleasure that I wouldn't give up in a heartbeat for it. But by the same token, on the other hand - I would literally rather never have sex again than to have it once and then taken away from me again. That's the reaction I have whenever this happens. And everytime, I go back to it like a dog that gets the occasional treat.

And furthermore - it dawned on me in the days after that night: that might have been the best night of my life. I'm 40, and I have had to wait this long for the simple pleasure of such intense physical connection, one that I may never experience again. It makes me feel completely sad. I don't know where to go from here. I don't know how to move forwards without being depressed and resentful of myself and my partner and her biology.