How to save myself from going out of service during my trade training

I am a pre alloted trainee in Indian Airforce.My trade is IAF(s) and this trade training is very hard due to hard physical standerds as compared to other Y group traids . Now i am in my traid training . In traid training i am already backphased two times on medical grounds and now in my third chance i am again medicaly down and now i am in low medical catagory. Now I am going out of service. I want to ask that why not they change my trade to another Y group traide Like clerical traids? Three years of my life are lost and i am in Air force from last 2 years. Please help me.is it my right to change my traid?