My first year of band in 6th grade I used a 7C, then around 7th grade I switched to 5C, then around 8th or 9th grade I switched to a 3C. I am a senior now. Until recently I've been using that 3C, but a few weeks ago I switched to a 1 1/2C and have been real tired constantly. I have to work twice as hard to get a high C out above the stuff, and it doesn't sound as good as it used to. I told this to my private teacher, and I think he said the switch from mouthpieces, especially one as big as the 1 1/2C would affect me a lot because your facial muscles are so finely tuned that the slightest adjustment will affect you. So is it possible that this mouthpiece is too big for me right now? Another friend who marched with Crown said that I just might not be using enough air to 'fill up' the mouthpiece and rely on too much pressure. I try not to use pressure and usually catch myself when I do it, but I need more help on how to minimize pressure. In marching band we do breathing exercises, but what do you guys think?