Forefoot Numbness

Lately when I go for a run, after about 2.5 - 3 miles, my right forefoot goes numb. Seems to be around the the mid to forefoot area. I have to stop and do CARS exercises. It'll relieve the numbness but after running another .25 to .5 miles, it will start to be numb again. I have been working on ankle strengthening exercises as will as arch exercises since I'm pretty flat footed. Any suggestions on what else I can be doing?