Welcome! You are wise to seek us out.
First of all, I would be very watchful of your difficult child since starting the medication. Keep track of anything that changes. Behavior, attention, anger, hunger, sleep, etc.
Second, I have found that my traditional parenting techniques, the ones that were natural and comfortable for me, just did not work with my difficult child. So, I had to try some things that I never thought I would, like detaching and picking my battles.
Also, be sure you get some ME time for yourself as it is draining to parent a difficult child.