......I have very little brake pressure when I step on the brakes
That sounds like TOW Vehicle brake issue vs trailer brakes.
I can't tell any difference in trucks brake pedal action whether towing or not seeing as how Trailer Brake Controller is ELECTRIC Signal vs a hydraulic
Now if you mean.........
Very little trailer brake 'action' then trailer brakes need:
adjusted
wire connections checked
magnets tested
and/or brake assemblies visually inspected.
Quick magnet test
Hold a compass down low next to drum
Have someone pull Emergency Breakaway Pin
Does compass needle deflect towards drum??
YES...adjust brakes
NO...check wiring/magnets