Burns and worsened hyperpigmentation from PicoSure laser, no improvement after 12 months

I had a few spots of PIH on my legs so I bought 6 sessions of PicoSure laser with FOCUS lens. After each session, my hyperpigmentation became increasingly worse and the spots grew 2-3x in size. Even spots that had no PIH blistered and scabbed. I expressed concern after each treatment but kept getting reassured by the Dr. that these were the expected results. The last two sessions were very painful for a week and caused my skin to completely come off as if it was burned. Why is this happening?