I do think this happens to a lot of people with anxiety. I do the same thing if I think I can't swallow or I think about swallowing too much. Or if I know there isn't a bathroom, I have to go. Do you have other things that indicate you have anxiety?
That if you don't do something to successfully tackle your anxiety problem you'll still have an anxiety problem. The breathing thought is just a thought, and it will eventually go away and then you'll get another one if you don't stop the problem. I know, easier said than done, but if you aren't in therapy with a psychologist who specializes in therapy that actually clicks with you it's something you should be doing. If you haven't tried CBT, try it once or twice or three times. And if you can't function, see a psychiatrist and find a med that can help in the meantime. But no, you aren't going to make yourself stop breathing, it's an anxiety attack. I hope you find a way to overcome this, I know, it's really hard. In the meantime also, you might want to increase exercise, learn relaxation techniques such as breathing exercises and meditation, and do everything you can to minimize the time you spend on these kinds of thoughts. And again, I know it's incredibly hard but keep trying anyway. Lots of people believe their thinking or actions can cause all sorts of things, but we're usually not that powerful. We can make ourselves miserable really well, though.