I'm 56 years old and was recently diagnosed with adult onset asth...

I'm 56 years old and was recently diagnosed with adult onset asthma and started on Singulair. I'm not a smoker, and never have been, but I've had a cough and other respiratory problems for the past couple of years. At first, the Singulair seemed to help with the cough, although I've had problems sleeping from when I began taking it. Also, in the past couple of weeks I've developed flu-like symptoms (I don't have the flu), and a severe sinus infection. I didn't realize these could be side effects of Singulair until I began to do some reading. I'm discontinuing the Singulair tonight, and hopefully these symptoms will disappear.