True North
I think you have had an excellent response to your question and agree with most of what has been said. However, I cannot belive that your instructor couldn't have shed some light on this issue. Are you sure you're not teaching yourself to fly?
For what it's worth, as an ex Glider pilot I used to be heavy on the feet when flying C150/152. The C150 doesn't have an adjustable trim tab on the rudder ( or at least the ones I am familiar with)and the C152 often get 'adjusted' by students who have forgotten their original walk round brief. However, it takes a pretty meaningful deflection before you would need boot loads of rudder to balance. Make sure your wings are level (equal sky!) then apply rudder as required to balance keeping the wings level.
I used to fly everywhere with one wing down and fight with the Rudder to keep the ball in the middle. Operator error!
Best of luck