Some would say it's a gift to be aware of the breath, as it's often used as an anchor, something that is ever present, that we can rely on to keep us grounded.
I can understand though that it would be frustrating to be aware of it all the time, especially to the point that it's causing you breathlessness.
I wonder what thoughts are still attached to this idea that you once smoked a cigar? Are most of them worrying thoughts? Often worrying thoughts can begin with "what if..?", "I shouldn't have..." "Why did I...?" It's possible that if you still have some of these negative thoughts attached that it's likely to be the thoughts that are causing your anxiousness rather than the fact that you are aware of your breath.
If this is the case, you might like to google Cognitive Behaviour Therapy. CBT is an approach used for anxiety that helps reduce our worries, negative feelings, and the negative impact of bodily sensations, by letting us come up with a less worrisome, more balanced way of thinking.
I also wonder if you have tried diaphragmatic breathing. This is a form of deep breathing that can help slow your breath and in turn your heart rate. Again you can google this. When we think of deep breathing we tend to think of deepening the inhalation, what this does is increases the amount of oxygen we take in, and increases our heart rate. A more comfortable approach is to lengthen the exhalation. This expels levels of carbon dioxide and balances the levels of oxygen Vs carbon dioxide. The longer you exhale for, your inhalation should eventually come to you quite naturally, without much effort.
If you want a relaxation tip, you could try progressive muscle relaxation. Have a look at "8 minutes to Calm" in youtube.
I hope some of these strategies are useful. They have definitely helped me when I've felt out of breath or panicked.