Whatever you did in the past is really hard to forget. Your husband did forgive you, but he could never get over the feeling of being rejected by you. So all he needs is your love and more care and attention. Although, I personally believe in actions rather than words. Just saying, "I am sorry" does not mean that the person is really sorry, and will never repeat the mistake, But still, sometimes this is just what the doctors order. You can go either ways. You can show that you are sorry with your compassionate behavior/action, or you can simply put that in words, or write down in a cute/poetic way in a greeting card. This is up to you. Anyhow, if words don't work, go for action. Slow and steady wins the race. You can slowly rid him of all the negative thoughts by your loving and caring attitude.
I went threw the same thing except it was my husband who cheated. He knows your sorry but the thought of what you did will always be on his mind its kinda like not really trusting you. We all make mistakes. Keep in mind think twice before you act if you have a great man at home don't lose him there hard to come by. I would make him feel like hes your everything. Call him at work tell him you love him, flirt with him. Try to make him feel good about your relationship. Good luck