Shoulder posture

i have rolled forward shoulders, when i pitch should i pinch my shoulders back throughout the motion and when i realease the ball?

When your shoulders are rolled forward its a strength problem. Pinching your shoulders when you throw is not going to fix the problem. Do more back strengthing exercises, specifically middle back exercises, YTWL’s prone cobras, face pulls, inverted rows etc. Also stretch the pec muscles as well as the lats. I would get away from doing any sort of bench pressing for a while and focus on push-ups for your chest. The push-up forces you to stabalize more and it also works the serratus anterior more directly, which will help your shoulder stabalize.