How to use different heights for IMC in C?

In my BMI calculation program (in C), you must enter the mass first and then the height (of n people). I would like to know why he is considering the masses correctly but is always using the first height to calculate.

#include<stdio.h>
#include<stdlib.h>

int main(void)

{

    float massa, altura, IMC;

    float *b=NULL;

    int counter = 2;

    int i, j;

    float somacounter;

    int counter1 = 0, counter2 = 0, counter3 = 0, counter4 = 0, counter5 = 0, counter6 = 0, counter7 = 0;

    b=(float*) malloc(2 * sizeof(float));

    scanf("%f",&massa);
    scanf("%f",&altura);

    b[0]=massa;
    b[1]=altura;

    int flag = 1;

    while(flag)
    {
        scanf("%f",&massa);
        scanf("%f",&altura);

        if(massa == 0.00 && altura == 0.00)
        {
            flag = 0;
            continue;
        }

         counter = counter + 2;
         b = (float*) realloc (b , (counter) * sizeof(float));

        b[counter - 2] = massa;
        b[counter - 1] = altura;

    }

   for(i = 0 ; i < counter - 1 ; i++)

   {

    for(j = 1 ; j < counter - 2; j = i + 1)

            {

                IMC = b[i]/(b[j]*b[j]);
                i++;
                j = i + 1;

                if(IMC<17)
                {
                    printf("\nMuito abaixo do peso");
                    counter1++;
                    break;
                }
                if(IMC>=17 && IMC<=18.49)
                {
                    printf("\nAbaixo do peso");
                    counter2++;
                    break;
                }
                if(IMC>=18.5 && IMC<=24.99)
                {
                    printf("\nPeso Normal");
                    counter3++;
                    break;
                }
                if(IMC>=25 && IMC<=29.99)
                {
                    printf("\nAcima do peso");
                    counter4++;
                    break;
                }
                if(IMC>=30 && IMC<=34.99)
                {
                    printf("\nObesidade I");
                    counter5++;
                    break;
                }
                if(IMC>=35 && IMC<=39.99)
                {
                    printf("\nObesidade II (severa)");
                    counter6++;
                    break;
                }
                if(IMC>=40)
                {
                    printf("\nObesidade III (Morbida)");
                    counter7++;
                    break;
                }

            }
   }

               somacounter = counter1+counter2+counter3+counter4+counter5+counter6+counter7;

               printf("\n\nMuito abaixo do peso: %d (%.2f )", counter1, counter1/somacounter * 100);
               printf("\nAbaixo do peso: %d (%.2f )", counter2, counter2/somacounter * 100);
               printf("\nPeso normal: %d (%.2f )", counter3, counter3/somacounter * 100);
               printf("\nAcima do peso: %d (%.2f )", counter4, counter4/somacounter * 100);
               printf("\nObesidade I: %d (%.2f )", counter5, counter5/somacounter * 100);
               printf("\nObesidade II (severa): %d (%.2f )", counter6, counter6/somacounter * 100);
               printf("\nObesidade III (morbida): %d (%.2f )", counter7, counter7/somacounter * 100);

return 0;

}