Side Stitches, No Good!

Started running tonight and was feeling really good and got into a rhythm right away. After about 20 min. I got a stitch in my side that just wouldn't go away! I tried walking, breathing deeply, and drinking some water. None of which helped. So I stopped, not my best choice but I'd rather do that then continue on for another 6 miles in sever pain and possible hurt myself more from poor form and not paying attention. Must run outside tomorrow and do some hills before my bigger race on Saturday!