Testing my faith

I am religious... I believe in God. But my faith is being tested! HOW can He be real if he allows mothers longing for a baby to endure the pain of infertility while all around them unfit mothers are fertile?

My sister is pregnant AGAIN with another baby she won’t take care of by another man who doesn’t take care of his.

I’m genuinely searching for a religious answer to put my faith back in check..