Laser hair removal stopped working after 4 sessions, what should I do?

I have had 4 laser hair removal sessions (laser, not IPL) on bikini, intimate area & underarms. After first 3, I was hair free for some weeks (1 month between sessions). I had a 6 week gap after the 3rd one& the hair came back. The nurse increased the intensity on the fourth session, which was v. painful. But no result: the next days I had the same kind of regrowth I used to get before starting the treatment .I have dark hair & pale olive skin.