Side Effects With Singulair in Children

My 10 year old son has been taking Singulair on and off for two years for his allergies, and the I started noticing that his behavior started to change. He was depressed, and he started shaking and making high-pitched noises from out of the blue. He would just be sitting watching T.V and out of nowhere he would start to shake, or do something that sounded like barking. I took him to the Doctor, and he tried to tell me that my son might have Tourette Syndrome. I went home and did research on Tourettes and nothing made sense, or matched to my child. All the while, I kept giving him the Singulair, and things kept getting worse. A few weeks ago, my husband heard on the radio that a news station would cover a story on Singulair and the side effects in children. To my surprise everything that my son was doing these children were doing. From the shaking (tremors), barking or yelping uncontrollably, and the behavior problems and depression. However, these parents stated that as soon as they noticed these signs, they took their child off of this drug and some of the symptoms stopped. My problem is my son has been off this medicine for three months now, and he still does it. The shaking, the yelping, and he is not the loving child I use to know. He still has mode swings, and he gets very sad then angry. His school is even asking question. I was wondering since my child was on this medicine for so long, could that have had some kind of permanent effect on him? I am so worried that my child has been changed forever. Can you give me some answers? Can anyone else relate?