I understand how you feel (although I didn't have to go through all you've been through).
I've have been so down since Angus has went to the bridge I've just wanted to cry every day & the last couple of days have seemed to be worse than ever.
Like you PT is not as fun as it used to be for me either. It just reminds me how much I miss Angus. And I guess it's because he was such a big part of my PT life.
So I am trying to spend alot of time with my girls. Take them for walks playing with them and just in general giving them all the love I would have give my big boy.
I hope soon that you'll find something to bring you out of this depression.