It sounds like a very bad case of anticipation. You're expecting a large recoil for some reason. The thing you have to do is convince your mind that pulling that trigger is no danger.

Just practice holding the rifle in the correct manner and getting behind it. Concentrate on your hold, and sight picture. And be sure to breath. Too many people get behind the rifle and take a deep breath, hold it, and then sit there. That never worked for me.

Then as you concentrate on the sight picture, pull the trigger back just to take the slack off it. When you get to that point, hold it there. Normally you will automatically fire it and it will be a total surprise. But if you have the right sight picture and the correct hold, you will hit where you were aiming.