When your husband decides to change custody, he will have to begin a new legal action, which means filing a motion or petition with the court. This is treated as a new suit, meaning he can bring in a lawyer if he doesn't want to continue pro se. whether or not the court grants him the change is another matter altogether. See family-law.lawyers.com/child-custody/How-to-Change-a-Custody-Agreement.html for more on this.
Cindy, If your ex and your child get along, it would be good for both of them to spend as much time together as possible. For me, I have not seen my daughter in over a year... it tears me apart and I know it has a negative effect on my daughter also. For the benefit of your child, let him have as much contact with his dad as possible... You can save yourself and your ex the trouble of going to court and spending all that money... Just sit down with him and discuss it like reasonable adults that both love their child. This is for the child's benefit, put your differences aside!