Kesha's mom has countersued Dr. Luke ... claiming he tormented and abused her by allegedly date raping her daughter.
Pebe Sebert claims in her legal docs -- obtained by TMZ -- Luke did indeed rape Kesha in a way "as not to be tolerated in a civilized society." She claims she now suffers emotional distress and post-traumatic stress disorder as a result.
Pebe is largely restating the claims Kesha has made -- that Dr. Luke gave her a date rape drug and raped her. But she also adds new detail, claiming Luke would brag about taking girls out on a first date, get them drunk and then "f*** them in the ass."
Pebe also claims Luke dealt drugs to entertainers -- which she says is how he acquired the name "Dr." -- during his 10-year run as a guitarist on "SNL."
Luke has denied the claims made by Kesha and Pebe, saying it's all a ploy for Kesha to get out of her contract with him.
As for the PTSD ... she says her blood pressure has spiked to 265/180 and during a therapy session she would become hysterical and convulse to the point where she had to be medicated.