did these pains come from increased mileage or what?

hi, i've been a runner for about a year and a half, without taking breaks. for the past couple weeks, i have been having problems with side stitches, it makes it difficult to run, and breathe. i always do the stretches that prevent them before i run, but they seem to have stopped working. i increased my milelage, would that have anything to do with why my sides are hurting? i keep a healthy diet and don't eat or drink to much before running. the side stitches feel worse than the regular side stitches that you get when you first start running, the feel worse and a few times i also had this feeling in my throat and upper body (mouth, throat, and chest) that it was on fire. what's wrong? and what should i do? i already so some ab exercises!