Mouthbreathing

I have a stigma to do with the fact that I breathe through my mouth rather than my nose. When I first started doing Pilates, a lot of emphasis was placed on breathing through the nose and I would either forget to do it or start inhaling desperately through suddenly blocked nostrils. When relaxed, as now, I can breathe quite easily through my nose but as soon as I start moving about, the panic sets in and my mouth opens. Embarrassingly, I found myself wheezing a few weeks back in Boxercise as the guy who runs it was yelling "breathe sensibly in through the nose and out through the mouth" to the group at large. I just can't get enough air in through my nose and then I start to panic when jumping about and boxing things. Having said that, the fact that I don't do it automatically is also a problem and in Pilates I would generally switch off and also forget to engage my pelvic floor and core stability muscles, which is like some kind of very-specific-to-Pilates crime.

However, I can understand and excuse these exercise things as the body under stress does funny things, what I do get worried about is what it looks like onstage and in real life (I can't believe that I put it in that order of priority). People who have their mouth open all the time look a bit dense, sad but true, and I really don't want my mouthbreathing make me look like an idiot, which is where the stigma comes in. Maybe I should tape my mouth up for a while so that I am forced to breathe through my nose. Cue line of people queueing up to help me out with that one. Suggestions welcome however. Teach me how to be like the cool kids with their nose-breathing skills.