Kesha -- I Spilled Sex Secrets About Dr. Luke to Rehab Doctors

Kesha spilled her guts to her shrinks in rehab about sexual and physical abuse at the hands of Dr. Luke ... so she claims.

Sources connected to Kesha's lawsuit against Luke tell TMZ ... when the singer went to rehab in January for an eating disorder, she "spontaneously" began telling doctors stories about Dr. Luke ... that he drugged her, sexually abused her and physically assaulted her. The sources say the doctors kept notes that will become evidence in her lawsuit.

The sources say Kesha's doctors advised her she needed to stay as far away from Dr. Luke as possible and one suggested she might die if she didn't heed their warning.

As for why Kesha never went to the cops, the sources claim Kesha had a Stockholm-type syndrome ... she had been with him for more than 8 years at the time, and she didn't have "free will."

As for Dr. Luke, his rep tells TMZ, "That's preposterous. Just because someone says something to a doctor doesn't mean they weren't fabricated or part of an overall pre-planned campaign."

The rep adds, "Her statements are false. It is important to note that these are just the latest in a series of bizarre public statements and actions by Kesha and her mother over the years, including Kesha's claim her vagina is 'haunted,' her drinking her own urine on her reality show, and her mother dressing up as a penis on the television show."