Are they measuring the movement in your SI joints, and noting progress? Or just applying the different modalities?
You mention a problem with your SI joints. I believe it's important to note the movement (via measurement) among other things, every session to determine progress. My son has recently undergone PT for back pain and a stuck SI joint - he said they measured the movement there every single visit. My current neuro massage therapist is a real problem solver with chronic pain, and she also measures my SI joint movement every visit (I also have problems there). She notes tightness, rotations, etc. before she begins.
There is a big difference between an individual approach to specific bodies and problems, and applying the usual "recipe" or modalities in a one size fits all fashion. I learned this rather late, but I recommend asking how they are identifying your progress (or lack of it). Too often it seems that x number of sessions with tens, laser, e-stim, aquatic therapy, etc. are prescribed without follow up until those sessions run out. It is a waste of time and $$$ without ongoing justification. In my humble opinion.