I can't add much more but I would reiterate that you've shown amazing courage just to open up on here, it's a step in the right direction. You're never a burden, this is so so important to remember! You have a relationship with your good lady and you've brought up, what I'm sure are three wonderful children, for that you should be proud of yourself. It sounds like you've done it against the odds as well which shows that you're a lot stronger than you think you are.
And I echo what @Izzy said, make another appointment, there's a reason it was cancelled and it was nothing to do with you. Having somebody to talk to will help!
This forum is always going to be here so feel free to just type your thoughts out whenever you need to, it really helps to get them down somewhere, let alone in a place where others who have felt the same way lurk.
It gets better!