I see a therapist weekly, and you need to as well.

It is also possible that you need some medication in conjunction to changes in lifestyle and diet.

I also would like to recommend you look into group therapy/support groups. I don't really have any experience with that, but I have elsewhere found a lot of comfort in knowing that others experience many of the same struggles, and I think that it can help to understand your pain and sadness though another's experience of their pain and sadness.

But, you won't like me saying this, but unfortunately it's not going to be optional: you need to start going on walks. Every day. 15 minutes min. No exception.