Help with Relationship- Relationship Problems and Advice

What do you consider the biggest problem you have overcome in your current relationship? The problem I am currently facing is that my fiance and I are getting married in October. He wants to have a child and I don't. I have been very honest about this with him. He says he is OK with it (We each have one child from previous relationships) and I am very content with that. I just wonder if this is going to become an issue in the future. I honestly think that he thinks I will change my mind and I seriously doubt that I will. I had a child at a young age. She is getting ready to turn 12 this year and I definately know that I don't want to start over again at the baby/diaper change.
What has been your biggest challenge and what advice would you give people on getting past that relationship challenge and making the relationship work?