Answer
Salam Dear Brother,
Thank you for your question and for putting faith in us to help you with your problem.
None of us is free from sin. Prophet Muhammad (peace and blessings be upon him) said:
“Every son of Adam is a sinner, and the best of sinners are those who turn (to Allah) in repentance.” (At-Thirmidhi & Ibn Majah)
Rest assured that there is always hope for believers to be saved from the hellfire as long as they admit their past sins and promise to never repeat them again. So do not be distressed. What you have done in the past was certainly serious, but it cannot be changed. What you do in the future, however, is up to you.
You must sincerely promise Allah that you will not repeat what you have done and then do your utmost to fulfill that promise. Ask Allah to guide you and to keep you strong in front of the evil suggestions of Satan. You must establish regular Prayers if you have not already done so and try to do as many good deeds as you can to keep from falling into sin again.
If you are sincere in your repentance, Allah will forgive all of your past sins and may even turn them into good deeds by His infinite mercy. Allah has told us in the Quran that He forgives all sins, no matter how serious, except for one.
That sin that He will never forgive is that a person dies believing that Allah the Exalted has a partner in His majesty. Associating partners with Allah, or shirk, is the gravest sin, and Allah will never forgive it if it is a person’s belief at the time of death. If a person turns away from this belief during his/her lifetime then He will forgive this as well.
Al-hamdulillah , you are a Muslim. Keep doing your best and never stop asking Allah for help. He loves to hear His servants asking for their needs to be fulfilled and He never tires of listening to our calls. 
I hope that this has helped you with your situation and I ask Allah the Exalted to purify our hearts from sin and to grant us Paradise in the Hereafter. Ameen.
Taqwa Saifulhaq, a former member of Ask About Islam (AAI) Editorial Staff adds:
The reply that was given to you by brother Waleed answers your question, but I want to bring together some points that might help you on your path of repentance.
Allah Almighty says what means:
{Say: O my servants! who have acted extravagantly against their own souls, do not despair of the mercy of Allah; surely Allah forgives the faults altogether; surely He is the Forgiving the Merciful.} (39:53)
So, it’s very important to know that Allah Almighty is The Most Merciful and His mercy is even greater than the mercy of a mother towards her own child. Allah Almighty doesn’t want to punish us for no reason. He called Himself At-Tawwab, The Most Forgiving, so when you repent you need to be absolutely certain that you have been forgiven of your sins.
However, repentance has its own conditions that you need to fulfill in order to be forgiven.
First, you need to admit your guilt and this is obvious in your words “My past makes me feel bad and guilty.”
Second, you must intend to not to do the same sin.
Third, you need to keep repenting to Allah, for the sins in general, for all humans commit sins always and to be certain that He hears you. Allah Almighty says what means:
{And your Lord says: Call upon Me, I will answer you} (40:60)
We are all humans and we all sin. That’s why we need help to prevent ourselves from sinning in the future.
- Think well of Allah that He will forgive you whenever you commit sins. Because when a person commits sins, then repents, then commit sins, then repents, etc., he will feel ashamed before Allah, which will cause him to feel frustrated and despairing. But Allah Almighty is The Most Merciful, and He will keep forgiving the people who keep repenting.
- You need to close the doors of evil. In other words, you need to keep away from the things that will urge you to commit that same sin. For example, you need to get closer to your beloved wife and be away from that woman with whom you sinned.
- Choose some good friends who will make you stronger in your beliefs. Try to memorize some verses from the Quran together, perform Prayers in the mosque, etc.
Dear brother, I believe that you need not to display what Allah Almighty covered. You did not need to tell your wife, nor that woman’s husband, because this will lead to many problems without being aware.
May Allah bless you and lead you to His own path.
Thank you for your question, and please keep in touch.
Salam.