Running a motor using Interactive C

The project is to design a robot out of legos which, by using infrared and breakbeam sensors, will follow a path of black tape on a white floor, pick up a block at the end of the tape, turn around, follow the tape back, and stop at the end. My issue is trying to figure out how to get it to recognize that it's at the end of the tape. At the moment, it backs up if it gets off the tape (which it does 15-20 times while actually travelling the track), so when it gets to the end, it just spazzes by going alternating forward/backward on and off the tape.
Any help would be appreciated, here's the code.

void main()
{
    int left_motor = 1, right_motor = 3, left_sensor = 5,
      right_sensor = 6, break_sensor = 2, back_count = 0,
      break_count = 0, motor_sensor = 0;
   
    while(1)
      {
        if(analog(break_sensor) > 200 && break_count == 0)  //if break beam sensor is broken, it will do this
          {
            motor(left_motor,100);
            motor(right_motor,100);   //moves bot forward
            msleep(300L);
            off(left_motor);
            off(right_motor);
            motor(motor_sensor,100);  //activates muscle wire, traps box
            sleep(5.0);  
            off(motor_sensor); //turns motor_0 motors off
            motor(left_motor, 100);
            msleep(500L);
            motor(right_motor,-100);    //this makes robot pull a 180
            msleep(500L);
            break_count++;   //exits the loop permanently
        }
        else
          {  
            if(analog(left_sensor)<120 && analog(right_sensor)>120) //left sensor off tape
              {                                                     //right sensor on tap
                motor(left_motor,100);
                motor(right_motor,25);  //turns left motor on high, right motor 25%, turns left
              }
            if(analog(left_sensor)>120 && analog(right_sensor)>120) //both on tape
              {
                motor(left_motor,100);
                motor(right_motor,100);  //both motors full speed
              }
            if(analog(left_sensor)>120 && analog(right_sensor)<120) //left on, right off
              {    
                motor(left_motor,25);
                motor(right_motor,100);   //makes a right turn to get back on tape
              }
            if(analog(left_sensor)<120 && analog(right_sensor)<120) //both sensors off tape
              {
                motor(left_motor,-50);
                motor(right_motor,-50);   //back up both motors              
              }  
          }
    }    
}