Stephen Collins -- 'I Am Not a Pedophile'

Stephen Collins says he's not a pedophile, but rather someone who had a "distortion" in his thinking.

Collins told Katie Couric ... he does not fit the "clinical or dictionary definition" of a pedophile ... so concluded his therapist. That same therapist, Collins says, told him that if Collins really was a pedophile ... he would have repeated the misdeed way more than he did.

Collins told Couric he has no attraction toward children and that the incident in 1973 -- where he made physical contact with one of the victims -- stopped him dead in his tracks ... saying, "It was the opposite of excitement or gratification."

TMZ spoke with that victim on Wednesday ... who feels Collins is downplaying the incident and doesn't buy his decision not to apologize to her.