At a crossroad - should I stay or leave?

I know that no one can tell me what decision to make but I feel like people here have a unique perspective that might be helpful. Sorry, this is long - I really need to vent...

I (42F) have been with my husband (41M) for 5.5 years, married for 3. When we met, he was a happy guy with a lot going on and it was clear that we had shared values and attraction. He has dealt with depression, anxiety, and OCD for many years, but he has always worked at getting better, including seeing a therapist weekly, for years, and practicing meditation and breathwork. I really appreciate his efforts.

Quick headlines of the relationship:

- Just after moving in together, he decided to go off his meds, because they have not worked for him in the past. That brought on the first deep depressive episode and I was caught off guard. I never heard someone say such dark things, and it was so hard. But it was temporary. (He hasn't agreed to start taking meds again since.)

- A few months later, his mother passed away suddenly. It was devastating on so many levels, and understandably it led to months of depression. But I really wanted to be there for him, and I felt that dealing with the pain together brough us closer. It definitely took a toll on me though, since I felt that I needed to take on his pain. I've learned to try and separate my emotions from his.

- I was doubting if I can manage this level of hardship but decided to get married because I love him and he can be an incredible partner.

- We started trying to conceive. Fast forward 2 years later and we've had 3 miscarriages (including one at 17 weeks), 6 rounds of IVF egg retrievals that have failed. For anyone going through IVF, you know how soul sucking and hard the process is.

So yeah, life hasn't been easy. And we've always had other issues around compatibility, whether about the way we travel, our passions, or sex drive. We are on our 4th couple's therapist because we both want to work at understanding each other better and improving our communication. Some of it has been helpful, and I've really been trying to change.

He wants to be heard and understood and not feel lonely and he shares how he's feeling with me - a lot. It takes up a lot of emotional space. I truly want to help him get better and find solutions. When I do that, he says that I'm not taking him seriously. But I have always been a "glass half full / everything will work out" type of person and I can't listen anymore to him saying that he will be lonely forever, he has nothing to look forward to, he'll never find community, etc. and not try to figure out how to change it. My empathy is turning into impatience and frustration.

Where we're at now: After my most recent failed IVF round, I understand that we will need to move forward with a donor egg, which is really hard. Also, he has made it clear for years that he will always be unhappy in the city we live in and he wants to move somewhere else, where he can find people/things that are more like him. I don't particularly want to move - I have friends and a life in our city. But if things were otherwise good, I would move with/for him.

I love him so much and he's a wonderful, caring, interesting person. Maybe I can continue working on myself to better understanding his depression and not feel responsible for helping him. But I feel like I would stay with him out of hope for a happy future, when the past experience only indicates that things won't change.

If I leave him, I might be losing my chance at becoming a mother. I don't know if at my age, following a challenging divorce, I could do it on my own (especially since it wouldn't be with my own eggs). But if I stay and we get pregnant, I'll have to take care of a baby and a depressed and anxious husband. I don't know if I have that in me.

I want happiness and lightness back in my life. But the change and thought of divorce is so daunting and scary.