What Causes Memory Loss And Tingling In Hands While On Levothyroxine?

I had a TSH of 72.5 last October and with taking Levothyroxine 100 mcg. daily, it is now down to 1.38 but I still feel sluggish, have numbness, pain, and tingling in my hands, weight gain, and brain fog. I an 60 years old and have lost my car in a parking lot three times in the last month! Twice at Walmart where I am very familiar! I have forgotten things my husband said to me as well as appointments. What is wrong?