Rachel Uchitel's New Crush -- Dr. Drew

In fact, we've learned -- it's Rachel's infatuation with Drew that led to her decision to do the reality show.

Sources tell us after Rachel initially turned down "Rehab" -- Dr. Drew wanted a personal sit-down to change her mind ... and she only agreed to the meeting because she says she has a mad crush on him.

So, now Drew has Rachel where he wants her ... and Rachel's got Drew right where she wants him.