My 8 yr old son has been on singulair for a year. He has complai...

My 8 yr old son has been on singulair for a year. He has complained with headaches and has missed several days of school this year with bar headaches. He recently started complain with pain in his right shoulder. My brother, who would be 33 today , died of lung cancer 2 years ago, so we are very cautious and nervous of any pain that cant be linked to an injury. Our family. Dr. scheduled us a MRI, but everything came back clear. We took him off the singulair about 3 weeks ago, because we suspected it was causing the headaches. Little did we know that it caused these other symptoms! He has not had a headache or any shoulder pain for about a week. I pray that there is no permanent side effects!