I just started taking singulair, It has helped the post nasal dri...

I just started taking singulair, It has helped the post nasal drip, cough and allergies. But, I feel very anxious after taking it and shakey in my hands and legs. I noticed my legs are weak. I have a hard time falling asleep at night, my body feels jumpy when I start falling asleep and I stop breathing in my sleep. I have never done this before the medication. I also get a medicine head feeling. and concentration problems. I am glad my allergies are cleared up, but I am not sure if the side effects are worth it. If I can't sleep again tonight I Am getting off the medicine.