S.B.
It may be that if he is truly ADHD, he is feeling "bad" at times. This is the age where you start knowing something isn't quite like it is for other kids and at this age, a common expression of this would come out as an "I hate . . ." phrase. Life as a true ADHD person is HARD and mood swings can be a part of it. Medication was a God-send for us because it not only improved what we could see behaviourally, but also he HE felt about himself. It isn't surprising that you are seeing this around times of transition - lots of these kiddos really suck at transition (wait until he starts modular classes and changes rooms at school every hour - *sigh*).
I wouldn't worry about counseling until you have had the screening done. There are TONS of resources once that happens - you could try visual therapy, occupational therapy, play therapy, regular counseling, nutritionists and dieticans, etc. Your options are limitless in the area you live in (I know, I used to live there with my kiddos). Remember, medication is only a piece of the puzzle . . . school intervention and your hard work along with medication will bring him a LONG way!
Good luck!