"How do I know it is clinical depression "

You do not. Self evaluation only brings you so far.

But from the little you shared - I doubt, it is clinical depression.

It "just" sounds like deep burnout.

You fought all you could and reached your self assigned goals - and now you see, it is not enough. There is something missing, but you lack the energy, to figure it out and fight for it.

The most important thing (for most) in life is people and not money. There seems to be your problem. Your potential broken marriage. Money for the sake of it is useless. Money is there to get you the things you want.

You have a house, but this was not what you really wanted. But maybe it was what your wife wanted?

A good therapeut can help with all of that. Figuring it out. A bad one just welcomes your money and plays your professional friend.

You probably lack real friends, you did not made or maintained, in your fight alone to reach your buisness goals.

It may not be depression. It could very well be stress and burnout. To start with: just to to any therapist (ie counselling psychologist or clinical psychologist), basically a therapist. You need talking, and then they can show the way forward. I may be wrong, but this is what I am doing as well.

Multi-million dollar business but can't Google?