I need advice. long post

I need some advice on kind of a touchy subject. I have been married for about 3 and a half years. It hasn't been a very happy marriage because we have fought really bad ever since before we got married.About 6 months after we got married it got so bad and he kept telling me to leave so I thought my marriage was over. I turned to another guy and started talking to him and ended up sending him nude pics but never actually met up with him. I felt horrible about it and ended up telling my husband about it awhile after it happened. No matter the situation between us I realize that it was a horrible thing to do and if I could go back and change it I would. We didn't end up splitting up and now have a 1yr old little boy but we still fight pretty often. My husband came home tonight from work and we had a discussion. He still has not forgiven me for my indiscretion that happened 3 years ago. I still love him and want my marriage to work out. He told me that he needs some kind of gesture from me to try and make up for what I did but I have no idea where to start. Do any of y'all have any advice?