what is causing low brake pressure? no leak of brake fluid anywhere.

Is your brake fluid dark or clear? If it is dark perhaps it was not flushed regularly and has brought moisture and contaminates around the brake hydraulic system. Brake fluid absorbs moisture from the air and causes brake hydraulic system failure if the fluid is not serviced approximately every two years. If the brake master cylinder is failing the pedal will feel poor, also after fitting new pads and shoes it may take a while for them to "bed in".