Must the marriage contract be renewed if a Muslim does not remember whether he intended to enter into the state of ihram for Hajj as a child, knowing that he got married while doubting whether he was still in a state of ihram?

As long as you are doubtful about having entered into ihram (definition) for Hajj that year, the default assumption is that you were not in a state of ihram. This original state is presumed to continue and is not changed merely by doubt. Al-Nawawi said: "One of the recurring principles in the chapters of fiqh is that if we are certain about the existence or non-existence of something, then we doubt its change or removal from its original state, we uphold the ruling of certainty and disregard the ruling of doubt." Based on this, your marriage is valid, and you are not required to renew the contract. Your Hajj is valid and has fulfilled your obligation of the Hajj of Islam, especially since the circumstantial evidence indicates that you had not entered into the rituals.