What is the diagnosis? Herinated disk? It seems that you do deadlifts without pain just builded up the fear. The best Treatment is everyday deadlift- maybe you are still doing deadlifts not in correct way and trying to lift more than your body can handle. Specialy than you neglet your back muscles for 30 years. If you can do deadlifts with 30-40kg without any pain- everything is fine :) just keep doing it :)