Levoxyl and difficulty breathing

I have been taking Levoxyl 137 for the past 4 months and have never felt so bad. Previously I was taking Levothroid. Over just the past couple of weeks the Levoxyl has been giving me some really bad side effects. On three occasions while driving I experienced very rapid heart beat, had difficulty breathing, tingling and numbness in arms and legs, and lightheadedness. The first time this happened to me I called my endocrinologist since some of these symptoms were listed as side effects and he told me that the low dosage could not give me those effects. So I thought I was possibly having a heart attack and went to the ER, and had some follow up tests with an MD. Both my MD and my cousin who is also an MD feel that it is the medication. I have now been changed back to Levothroid 112. Let's see if the side effects disappear. Good luck to all visiting this site.