You need to be waving your intensity efforts. You cannot just do 5-8 singles every week and expect to add weight. I LOVE heavy singles across for Presses, but not week in and week out.
Take your 1RM and set up something that looks like this as a starting point:
Week 1: Vol 70% (5x6 or 4 x 8) Int 85% 3-4 x 3
Week 2: Vol 75% (5 x 5 or 4 x 6) Int 90% 3 x 2-3
Week 3: Vol 80% (5x4 or 4x5) Int 95% 5-6 x 1
Bump up weight a little each cycle on both days