4y symptoms and conditions

My 4y/o son has asthma that was not well under control, so the doctor put him on Singulair and Flovent about 2 months ago. In the first few weeks, he started having severe leg pain. He would be up at night crying. I would massage his legs till he went to sleep. He also started soiling his underwear with small thick amounts of stool multiple times a day; despite the fact that he has large soft bowel movements at least twice a day. His asthma has been well controlled since the start of the medicine. We stopped the Flovent 1month ago to see if the Singulair would continue to control his asthma, which it has. We adjusted his diet, since the doctor attributes his stooling to constipation, which has not helped. He is now frequently peeing his pants and frequently complains of arm and leg pain which comes on suddenly and seems to last for 5 to 15 minutes. I am going to take him back to the doctor for a full check up to rule out anything more serious, such as a spinal tumor, but till then I am going to stop the Singulair and see how things go. I wanted to stop it as soon as the incontinence started, but was afraid of his asthma flaring back up. Is flovent causing anyone's kids any issues. My son also seems to be having trouble getting his words out.