Could Severe Fatigue Along With Loss Of Memory Be Due To Levothyroxine?

I am on Entyio for Crohn s. Dr. says this is not the cause of my EXTREME FATIGUE. I switched to levothyroxine because of the cost of synthroid, have been on for a yr now. But the fatigue, depression, memory function is not good. Text done and increase of dosage but I feel worse. Would switching back to syn.. be prudent?