Happiness depends on a lot on what you truly want, as opposed to what you want to want, so I'd encourage you to get familiar with where those diverge. E.g., a lot of people want to want to get rich, but as you've discovered, more money doesn't actually leave them more fulfilled. If you're finding that hard to discover, a good therapist can help a lot, as talking with a lot of people lets them see patterns an individual can't.

Personally, I am also not great at telling when I'm stressed. So I've learned to look for obvious correlates. As an example, I am normally the sort of person who spends change. That is, I generally don't have more than $1 of coins, as I use them to make purchases. But when I'm stressed or depressed, I'm less likely to take the time to count out change, so I end up with an increasing number of coins on my dresser. That's a sign to me to ask what's wrong.

Also useful to me has been tracking the number of steps per week. I have a Garmin running watch I never take off. If I'm stressed, I'll become more sedentary. That's not just bad for my long-term health; it also decreases my resilience in the face of stress.

These things sound small, but they're useful to me as clues to the bigger things in life. If these indicators tell me I'm not doing well, I'll go down a mental checklist of things that could contribute. Am I sleeping enough? Eating well? How much alcohol am I drinking? How much sunlight am I getting? How do I feel before starting work? After the first couple of hours of work? At the end of the day? How are the important relationships in my life?

With that mindset, you can turn it into a debugging problem. E.g., if being too sedentary is one hypothesis as to why you're not happy, there's lots to experiment with there.