Your prayer has come before God with a humble and honest heart, and He hears that kind of prayer. To feel sorrow for walking away and to say I do not deserve forgiveness is the beginning of returning to Him.
Know that His mercy is greater than your sin. The Lord Himself taught those who already believe to pray, forgive us our debts, to show that even after we have been washed, the way of repentance remains open. It is not taken away. When we remember our sins, confess them modestly before Him, and ask for pardon, He is ready to forgive. What is impossible is to be washed a second time as at the first, but it is never impossible to be renewed by repentance.
God in His patience does not strike at once, but is longsuffering so that He may lead you to repentance. He waits, not because He overlooks sin, but because He desires your return. This sorrow you now feel, if it is a godly sorrow, works repentance unto salvation without regret. It is not like the sorrow of Esau, who wept out of pride and anger and did not truly turn, nor like Judas who despaired. It is like David, who after his great sin washed his bed with tears and confessed, and through that confession became better than before. So you also, by continuing to acknowledge your sin before God, become humble and ready to receive His remission.
Therefore do not stay in despair and do not turn back from this good beginning. Enter fully into the thought of your sins, confess them plainly to God, and bring forth fruits worthy of repentance. That means turning from what led you away, seeking Him daily in prayer, hearing His word, and walking in obedience. As you ask God to forgive you, forgive others also from your heart, for the Lord has joined these together. And let your repentance show itself in deeds of love and mercy, for almsgiving and faithfulness help to cleanse the wounds of sin.
You are right to come only through Jesus Christ, for there is no other name by which we are saved. It is His cross that makes forgiveness possible, and it is His blood that washes us when we repent and believe.
I pray for you now that God will forgive you according to His abundant mercy, lift the weight of this tough situation, and make things right in the way that is best for your soul. May He give you a firm purpose to stay near Him, strengthen you to bear what you must bear, and lead you to peace with Him. Keep praying, keep turning to Him, and trust that the One who taught you to ask for forgiveness delights to give it when you ask with a true heart.