Do your instructors share with you what they've written in your student records? That will give you clues as to what you need to do to get your landings right - especially if you find that several different instructors all say the same thing!
Don't worry too much about not getting the landings right - lots of students who are otherwise good learners get stuck at this stage, then one day it just "clicks". In my experience the most typical faults are:
1. Unnecessary aileron inputs on short final, leading to inability to stay on the centreline (solution: keep wings level; use your feet only for directional control)
2. Not completing key tasks (full flap; RT call; final checks) early enough, leading to overload/distraction from keeping to the glidepath (solution: get configured and accurately trimmed for the speed as early as you can)
3. Insufficiently consistent and accurate visual scan (should be "Runway numbers - airspeed - runway numbers - airspeed" all the way down final, with small power adjustments in response to changes in flightpath)
NS