Gel caps symptoms and conditions

My son is 10 years old and has been on 5 mg. singulair for 3 years. He has been getting frequent headaches,and is in the bathtub right now screaming with one! Also alot of depression.I just came upon this website accidently ,by searching the internet for what might be causing such headaches in a child. I was shocked at all of these symptoms! I am not going to give him any more singulair.But what is everyone doing to replace it and deal with their kids asthma problems? My son has had so may behavioral issues and being so unreasonable and always thinks were picking on him.To extremes! Very hars to deal with,constantly! TC