I Was Given Mirtazapine As A Sleep Aid To Get

I was given Mirtazapine as a sleep aid to get me off Lorazepan that I have been taking for 30 years with no adverse effects but, my new Dr doesn't want to have me continue them. I took the first mirtazapine and 20 minutes could not keep my eyes open so I went to bed and soon the agition started and it felt like I just had 3 cups of strong coffee, couldn't stay in bed. Have been up walking around and unsteadly, trying to get this to wear off but, not much success, any suggestions on how to get it to pass.