Oh the ole stitch in the side. You are getting this because you are not breathing properly. You have to make sure to inhale and exhale when you work out. You get a stitch in the side from not supplying enough oxygen to your body.
I learned this when I was in the service had to run every single day I even would get it on the elyptical machines. Once I found out what it was and started paying attention to how I was breathing it went away. Thus the reason when we ran in the service in groups we would sing a cadence it helped us to breathe.