Stitches

sometimes when I throw long toss or I pitch I get a stitch on my pitching side, it really cripples me and I find i hard to throw through it, although its never happened to me in a game
I’m not sure why it happens I think I migt not be breathing right or something.
any advice?

ive had one of those before. hurts like a *****. i think its becuase a muscle wasnt properly stretched in your core.