Serveral weeks symptoms and conditions

I posted serveral weeks ago about taking my 5 1/2 yr old off singulair. He has done great as far as the asthma, no problems what so ever. The main reason I took him off was due to his behavior. Very moody, hyper, aggitates easily and so on. Well, after the 2nd week, he was like a NEW child...very calm and behaving in school. Well, he has pretty much regressed back to the behavior before taking him off this med. He has now been off of it for 5 weeks. His teacher asked me last week, if I had to put him back on this med, because he was getting back to his old ways.
He is currently going the an evaluation for ADHD. I have stuggled with the fact that my son may suffer from this and have tried almost everything to avoid medicating him...I was really hoping this was the culprit to his behavior..He had been on singulair for over 4yrs...Is it just going to take longer to see the full effect of NO SINGULAIR???