That sounds pretty grim and I'm sorry it happened to you. Having to be strong for other people is damned tiring.
I'm no psychologist, but that sounds a lot like depression and if so, would explain why there's little passion to be found at such a time. Certainly when I've had periods of clinical depression, life was pretty damned bleak for a while. As you say, you can't chase happiness or force it to happen. Anti depressants helped me, but I found that they certainly didn't encourage passion or enjoyment in anything as they takes away the highs as well as the lows.
Sounds like you've got a good partner and that's half the battle. I hope things improve for you soon.