yes. the statute gives the court power to modify support back to the date of notice of the motion to modify. so if you have not yet sent notice to the other side, the answer is no.
call the clerk, get a court date. send notice that you want a hearing to reduce your support on the attached motion filed--insert the date.
Why is there no hearing date set? Did you file a notice of motion with a date set for hearing? A motion by itself is on file but no hearing set. You need to set a hearing date.