Side stitches/ running cramps

Hi! First time marathon runner here, training for NYC currently. My biggest hurdle while training has been side stitches right. It feels like a stabbing pain on my ribs. I’ve done a great deal of research on the matter and think it has to do with breathing. I’ve tried focusing on my breathing at the beginning of every run. I inhale through my nose and breath out through my mouth, while being cognizant of taking deep breaths through my stomach instead of chest... that normally does the trick but hasn’t solved it completely. Sometimes it gets so bad I have to stop my run. Has anyone else ever experienced this? What has worked for you?