I am not sure if the mention of depression was medically diagnosed or you have come to that conclusion yourself, i dont mean that to sound condescending.
I was diagnosed with depression last year at 42, first time in my life with no previous history, i am a very happy go lucky character usually, hence it was a very alien concept to me! No one thing had bought this on, maybe just a culmination of things over a couple of years. I was given options, drugs, counselling etc but decided to try and do it without drugs and just the support of family and friends. My life was/is good, just there was something there i couldnt shake and no matter how much i knew my life was ok, although things could be better of course, i just couldnt feel happy, even though i desperately wanted too. It was a massive eye opening experience.
I mention all this with a caveat to what i have read on your post buddy.
Under no circumstances put your future happiness/well being in the hands of someone else. You MUST be happy with yourself before you can offer anyone else a future imho.
I wont express my personal views on your partner (ex or not) as you probably wouldnt want to hear it.
Get YOURSELF happy buddy and when you are happy you will always know you can be happy with or without anyone else