hi Nervous, we all make mistakes, sometimes we don't want to, but misjudgements, underestimating or perhaps forced errors is what we have to expect, whether we like it or not.
What ever was the reason you and your wife divorced/separated is of no consequence, however you broke the trust of your girlfriend and had a fling with another person, so you're been struggling for 4 years, that's too long and really long enough, so you have to get yourself back on line and start again.
Your wife dislikes you, but that's now history, and the only affiliation is your daughter, but that's OK you can rebuild your relationship with her, even if she lives interstate, or as Tony has said you could move much closer to her.
You know we struggle through days not wanting to make any contact with other people, and that's exactly how depression operates, it controls us, so what we have to do is to break any link to this illness that is keeping us in depression, easier said than done, I know.
One good reason why you haven't found another girlfriend is because you're not allowing yourself to be free, and it is hard when you are depressed, so you have to begin treatment, it is hard and difficult to start with, but when you feel the way you are now, you can't go any lower.
Your doctor will understand that you are suffering from depression, and there's no way you can disguise it from him/her, they are trained and can tell by looking at your eyes, so please can I suggest you contct him/her. Geoff.