I'm a non-ADHD partner and I'm honestly at a loss...

I have been with my partner for around 2.5 years, and we currently live together. When we initially started dating, it was a whirlwind romance... we unofficially moved in together after only a month, we were so in love that we talked about our future constantly, and we officially moved in together about 6 months into our relationship when both of our leases were up. 

I love my partner more than anything. I see what an incredible human being he is, and that he does always have the best intentions. I've never felt so safe in a relationship but also so unsafe because of the ADHD. Covid hit around 4-5 months into our relationship, and like so many others, we have really been put through the wringer from job loss to egg freezing to losing oneself in their work. Our sex life is struggling to put it mildly, which has brought on its own significant issues, mostly for me. I feel like I am the only one fighting for our relationship, and I honestly don't know how much longer I can keep fighting. We have conversations around "change" and how we're going to do better at least once a month, and I'm exhausted from it because nothing ever changes. The intention is there and he'll try for a week, maybe a few weeks, only to have him never follow through on anything. Whether it's therapy, working out, cutting back on work hours, etc. it only lasts for a blip before we're right back to where we started. I've recommended couples therapy, I'm over here reading books about ADHD in relationships (which we promised to read together, but you guessed it, he hasn't even touched the book), and I'm working on bettering myself in hopes that he'll see me getting better and will want to do the same. 

I want this relationship to work, but I don't know what else I can do or how to find sustainable change in our relationship. I'm older than him and am sadly on a bit more of a time crunch when it comes to kids, and I feel like our relationship has completely halted because he's in this slump he can't/won't get himself out of. I've grown angry and resentful that our relationship isn't where I feel like it should be, and that I'm the only one who seems to care about getting us to a good place. 

What do I do?