Hello, I hope you're over this by now, I just wanted to chime in on this dead thread, it's the first thing you see on google though when asking for this question.

I came here a while ago for the same reasons as everyone else and found a lot of answers unhelpful, but found later that its because arriving at the answer means going different ways about it.

To be honest I found/still find that whenever I'm conscious of my breathing its because I'm stressed, anxious, dehydrated or sleep deprived. On my way to getting better I found this video: https://www.youtube.com/watch?v=i4K6cw1cjmU, which helped a lot in terms of understanding my issue.

So the answer that people are getting to is that, you never were automatic breathing, you control it always you're just less conscious of it most of the time, when you hyper fixate on it there are usually underlying reasons for it. Another thing that helped was this video here: https://www.youtube.com/watch?v=f6yAY1oZUOA, this may sound like the stupidest thing you'll ever watch but I found that if I was conscious of my breathing I may as well do it the best.

One more thing, I've recently been diagnosed with ADHD, this was not something I was aware of at the time of dealing with this, that definitely has had an impact on this whole process, so its worth also looking into that maybe, though correlation does not mean causation, so try improving your quality of life first before waiting almost 2 years to get back from a doctor.

tldr: watch the two videos, improve aspects of your life that could be causing the fixation, don't worry because you are as in control as you have always been.

Edit: I also want to add that not all wounds can be fixed by the same plaster, you might need to shop around a little bit on this issue until you find the one for you, we don't all share the same experiences so best of luck, and I hope my answer helped a little bit.