I start itching 15 min into swimming but only in my own pool. We had chemicals tested and all was normal. What could cause this?

Combined Chlorine. Often in home pools, the combined chlorine (bound chlorine) can be quite high. Free chlorine is active chlorine, but becomes "bound" when it kills bacteria etc. This is what will give the pool a chlorine smell and also what often causes the water it to get "cloudy". In my experience, getting the combined chlorine down will help your problem. Test for combined chlorine and go from there.