Replacing Ann Curry has gotten Savanna Guthrie stressed out. The Today show co-host is suffering from head-splitting migraines barely a month into her new gig, sources say. “She goes to a doctor two days a week for treatment of the migraines, and is required to wear dark glasses when she’s not on set,” a source tells the New York Post. “The pressure of taking over after Ann’s execution is taking its toll.” Today's lackluster ratings could be related: Rival Good Morning America beat them by more than 300,000 viewers during Guthrie's first week. (More Savannah Guthrie stories.)