on my last two runs (wed and today) i got a cramp right below my rib cage on the right side. i've never had a problem with this before but both days i started cramping up just about a half mile into my runs. i tried to run through it but after about 2 miles or so it was unbearable. today i walked for about 5 minutes then did another mile and called it quits. any idea what could be causing this?