Singulair and stimulus

Hi everyone
My little boy who is nearly two was put on Singulair as a preventative.
I did check on forums when we started using Singulair and I was concerned that there has been descriptions of negative affects. Always trying to be objective I rationalised that the people in this forum are a small part of the greater Singulair population and as a result there was a low risk of negative affects on my little boy.
I have to say I think I was wrong. As soon as he was using Singulair, he had restless nights of sleep. Every night he would cry off and on until 2am and I guess he was so tired he slept. During the day he was very short tempered and became upset very easily. We put this down to tiredness. After 10 days of the lack of sleep for parents and little one, we told our doctor.
He advised to take him off Singulair for 5 days and make observations and then put him back on. Last night, his first night off Singulair was bliss. Not a sound. He had a great sleep. As I type he is now having another great sleep.
Let us see what happens after 3 more days and after putting him back on Singulair.
It would seem that if we are correct and that Singulair is a cause of an issue for my child, am I a quasi beta testing laboratory for a drug?
We are from Australia.
Thank you for reading.

I just started using Singulair a few days ago. I am 54 years old and just started coughing at night only. I would be fine during the day and then never failed, at night I started to cough keeping me awake. I was given antibiotics, narcotic cough syrups but it only helped temporarily and then I went back to coughing nights only again. So as I mentioned, I started taking Singulair a few days ago because my physician thinks I have developed allergies and Singulair is noted to help night coughs. It is helping my night coughs but I still cough a few times at night and now I cough quite a few times in the day when I never use to cough in the daytime. Wondering if Singulair is worth taking as the symptoms are becoming opposite? I hate taking drugs and don't know if I should find a safer alternative? Help, anyone? Thank you