Yes, I can understand your feelings -- but most important, God understands them and wants to heal them. One of the reasons Jesus was sent into the world was "to bind up the brokenhearted" (Isaiah 61:1).
God could have healed your baby in response to your prayers, and I don't know all the reasons why He didn't. Human suffering is a mystery we will never fully understand until we get to heaven. But this doesn't mean God is indifferent, or that He doesn't love us or care what happens to us. Even when life seems to turn against us, we still can trust His love and look to Him for the strength we need. The Bible says, "Whoever is wise, let him... consider the great love of the Lord" (Psalm 107:43).
Right now, I sense you are deeply disappointed -- disappointed with God, and disappointed that your son isn't the perfect child you'd hoped for. But listen: God entrusted this child to you, and I pray that in time you will come to see him not as a problem, but as a gift.
Pray, therefore, that you may become everything your son needs for you to be -- not just in your provision for him, but in your love and patience and kindness. Most of all, ask Christ to fill your life with His presence and love, and then turn to Him every day for encouragement and strength.