Deadlift Nationals

Hello. I have competed for Nasa-Sports Powerlifting since 2014 and have placed 1st each time. I will soon be attempting a national record in October for deadlift. What is a great routine to develop more strength? Before I was doing my max to often and I didn't feel much strength increase. Right now im on a 3x3 and 5x5 routine and have noticed some differences. Any advice would help. Thanks!