If a judge signs off on an order for less than the guideline amount set by the state formula then the party receiving support can essentially ask the court for a modification up to the formula amount without there being any changes in income or custodial time. Otherwise in order to get a change in the amount, there needs to be a change in circumstance from when the initial order was made. This change in circumstance is usually someone making more money, less money, or the visitation arrangements changing. All of those circumstances could drastically change the support amount.
The amount of support does not just automatically change because you get a court order changing the custody and visitation arrangements. It is the responsibility of the parties to either agree to a modification and file it with the court or to request an order from the court to modify the child support. You will only get a change in support from the date that your motion (request for order) is filed with the court, so it is important to act sooner rather than later.
If the Department of Child Support Services is involved in your case already then you should contact them to help you make changes to the support amount. If you need help enforcing or establishing an initial order for child support, that is something that you your county's Department of Child Support Services can help with as well. However they do not aid in establishing spousal support, creating a custody and visitation order, and many other issues that you should hire an attorney for.