Cannot register Collision from behind.

Hey there, I got a small problem: I am currently working on an enemy script for my 2D Game. While most of it works fine, I cannot detect the collision between my character controller and my rigidbody, when the character controller hits the rigid body from behind. to be more specific, rigid body moves to the right, character controller stands right hand side of it or moves to the left --> collision.

Rigidbody moves to the right, character controller stands left hand side and runs into the collider ( both moving to the right now) no collision....

 function OnCollisionEnter(collision : Collision) {
 
         var contact : ContactPoint = collision.contacts[0];
         var pos : Vector2 = contact.point;
         if (collision.gameObject.name !="AvestasDummy"){
             
         
             if(pos.x>transform.position.x && pos.y>transform.position.y-(0.5*transform.localScale.y-0.1) && facesRight){
                 currentSpeed=currentSpeed*-1;
                 facesRight=false;
                 }
             
             if(pos.x<transform.position.x && pos.y>transform.position.y-(0.5*transform.localScale.y-0.1) && !facesRight){
                 currentSpeed=currentSpeed*-1;
                 facesRight=true;
                 }
         }
         else{
         
             if(pos.x>transform.position.x && pos.y>transform.position.y-(0.5*transform.localScale.y-0.1)  && !Gesammelt.gotDmg){
                 
                 if((!dmgFromBack && facesRight) || dmgFromBack){
                     Gesammelt.avestasLife-=1;
                     moving2.knockBackRechts=true;
                     }
                 }
             
             if(pos.x<transform.position.x && pos.y>transform.position.y-(0.5*transform.localScale.y-0.1) && !Gesammelt.gotDmg){
                 
                 if((!dmgFromBack && !facesRight) || dmgFromBack){
                     Gesammelt.avestasLife-=1;
                     moving2.knockBackLinks=true;
                     }
                 }
             }
                 
 }

the characterController's name is "AvestasDummy"

Anyone got an idea? :)