Yeah same here
i try doing a little bit of breathing excercises before i play during our show and it helps
plus our director has us do concert f for 4 then breath for 4 and it seems to help sometimes occationally you could add 4 counts to how long you play the f while leaving how long you breath at 4 every time it helps a lot with lung capacity, loud crecendoing (spelling?) notes, long tones ect. ...