I'm really sorry OP. I truly am so sorry for what you're going through. I also feel like that often. "I can't go on." But then I go on. Because it's too important to us not to. We'll go on until we can go on no more.
In my view therapy is essential, if you can access that. There are lots of therapists around who specialise in infertility, and can help you to process and clarify your feelings. I also find podcasts helpful. I recently started listening to one by a support group called Uniquely Knitted. The host of How to Fail has also spoken a lot about her coping with infertility, she's very strong, confident and wise about it so i'd recommend tracking her down too. It really helps me with feeling less alone, as this is such an isolating journey.
Do you have any hobbies? I started yoga and reformer pilates last year, and it's really helped me with keeping my body image in check. Reminding myself that I'm physically strong and fit and healthy, and can still be that regardless of my fertility struggles.
And finally - I remind myself every day that this is just a chapter, and regardless of the outcome, it WILL end. I'm a bit older than you at 40, so realistically it's just a few years left for us. Which is scary, but also relieving in a way. This helps me in a few ways - reassurance that however hard it is now, that's going to end someday and I'll be so resilient from this journey that I'll be able to cope with the grief if things don't work out to plan. And it also makes me determined to approach this chapter with as much hope, love and positivity as I can muster. I struggle to hope sometimes, but if i'm only doing this for a few years - I may as well go all out, right? I may as well dream about my baby, visualise it all working out, advocate for myself and do everything that I can during this time.