I Have Been On Singular For A Year For Severe

I have been on singular for a year for severe asthma I have become unable to sleep at night, increase depression,feeling very tired,no energy, and recently having a pain and closing in feeling in my neck- throat I went to the dr today and they did a ultra sound on my neck and it was good, so no blockage. since I got home I have been looking at the side affects of singular and have noticed quite a few that I have. could this medicine be causing these problems in my neck-throat? Also, can I quit this suddenly or do I need to taper off slowly. thank you. YYYY@YYYY