Few sins are as destructive and cruel as the one your husband has committed, and my heart goes out to you. It's no wonder the Bible says that adultery is "bitter as gall. ... Whoever does so destroys himself" (Proverbs 5:4; 6:32).
It may be hard for you to forgive your husband for what he did - but what if you don't? Instead of forgiving him, what if you allow your hurt and bitterness to keep festering like an angry sore in your mind and heart? You know the answer: Your pain will only grow more intense, and your relationship will be poisoned. To put it another way, your home will become a battleground instead of a place of happiness and peace. Do you honestly want this? I doubt it, in spite of your present feelings.
The fact that your husband admitted his unfaithfulness suggests to me that he is genuinely sorry for what he's done; otherwise he probably would have just kept quiet. Let his regret be the first step in healing your relationship.
Then ask God to help you forgive him for what he's done. The key is to realize how God forgave us - not because we deserved it, but because in His grace He loved us and gave His Son for us. The Bible says, "Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you" (Ephesians 4:32). Then ask God to help you rebuild your relationship by putting Christ at the center of your marriage - and your lives.