Did the fitter actually measure your pelvis?

(you lie on your back and hug your knees, and he palpates for your sit bones - or has you palpate for them - and measures the actual bones themselves)

There are butt-o-meters (you sit on it and make dents) that can put you in the size ballpark, but they don't give a lot of information you really need for proper saddle fitting.

Either your saddle is too narrow, too padded, or too tilted up at the nose. Or your posture is too sagged so you are going into an anterior pelvic tilt. Or the saddle just s*cks.

If you've got a fitter, he should tweak your fit for free for the next year. Give him a call and tell him there is a problem with the saddle he set you up with or the way he set it. He'll fix it, his reputation is hanging on that!