Good luck, I can relate.

Happiness is an emotion. It is next to impossible to explain what an emotion is like for one person and then compare it to another. The only thing we can do is see what made some others happy, then analyse your feelings in those situations and decide for yourself that that is most likely happiness.

The thing is with this and any other emotion, you can't describe it to others. Metaphors, physical sensations, the descriptions of certain situations. all good attempts, but none actually succeed. It's like trying to describe sight to a person who can't see, or sound to a person who can't hear. Completely impossible.

And this isn't for a lack of trying. I have been having trouble myself figuring out emotions for most of my life as well, and I still don't really know. I have in the end decided that certain sensations in my head that appear in certain situations are emotions. As long as I keep track of them, and also on every other part of my body and how it is acting, I will know what I am feeling when.

So I guess my advice about figuring out happiness is to decide what you want to be happy with, then say that you're always happy then? I honestly don't know beyond that.