I have been practicing shedokan for last two years. But unfortunately I stated my training at an age of 21 years (Now I'm 23). Consequences I am facing of starting this much late is that my legs do not stretch enough to throw a proper round house kick. When I started my training 2 years back. I could stretch my legs almost 110 degrees apart. Now can stretch them almost 120 degrees apart.
When I perform stretching drills, I feel severe pain near ball joints between my legs and pelvic bone toward outside of my leg. It feels that there is some lock that prevents my legs from being stretched. Whereas I do not feel any stretching effect on the inner muscles of my leg. My instructor does not understand my condition and keeps saying, "You should keep on trying and one day you will be able to have a full stretch."
So my question here is simple. Is there any drill which I can perform to increase my stretching? Or I will never be able to gain any further stretches?