Johnny Carson's longtime lawyer is blowing the lid off the secret life of the beloved "Tonight Show" host - painting him as a sad, depressed man who cheated on his wives, was tormented by his mom and refused to visit his son in a mental hospital.

Henry Bushkin - who was jokingly dubbed "Bombastic Bushkin" by Carson on his late-night NBC gabfest - told Page Six about a 'warts and all' memoir he's pushing about the late night king.

Among the revealing details:

• Was so miserable at the top of his game that he constantly "questioned his own ability to have happiness in his life."

• Enjoyed the use of a 10,000-square-foot penthouse with a private pool at Caesars Palace when he played Vegas and routinely entertained the "18 beautiful girls in the chorus line that opened his act . . . and he was certainly involved with some of them."

• Refused to visit his son, Rick, when he was committed to Bellevue with severe emotional problems. "The kid was there for 4½ months and he never went. I had to take care of everything and was there almost every day. Rick [who died in a car crash in 1991] was a lovely human being."

• Abandoned many of his closest friends, including Bushkin, who says, "At one time we did everything together. At the end, he treated me like everybody else - like I didn't exist. At the end, it was like I was an irritant. In many respects, he was the saddest guy I ever knew."