Suggest Treatment For Lack Of Concentration After Taking Nortriptyline

Hi there I am taking nortriptylline for nerve pain following a 3rd recent microdiscectomy. Since starting them 2 days ago (10mg 3 times a day) I can t think straight or concentrate and I m finding it hard to speak, it s as if my brain is lagging behind and I can t form the word or think of the word I am trying to say? Should I stop taking them?