“DUCK DYNASTY” reality star Phil Robertson, once a poor Louisiana redneck, built a stag­gering $70 million empire selling duck calls and hunting accessories – and now he’s hauling in another $5 million as author of a sensa­tional tell-all.

His new bio “Happy, Happy, Happy” soared past Facebook boss Sheryl Sand­berg to top the nation’s nonfic­tion best-seller list after selling out the first print run of 300,000 copies – BEFORE it was even released.

But fans of the entrepreneur’s popular A&E show are stunned by his revelations of shocking drug secrets, violent fights and a cheating scandal.

After turning his back on a poten­tial pro football career in the 1960s so he could pursue duck hunting, Phil’s life spiraled out of control.

He confesses he stayed “ripped for eight years” on whiskey, beer, marijuana, pep pills and speed. “We got drunk on anything we could get our hands on – running wild and duck hunting,” he writes.

The 67-year-old clan patriarch married his wife “Miss Kay” when he was 16 and she was just 15. Even though they had three young chil­dren, Phil admits: “The only thing I seemed to be wor­ried about were how many ducks I could kill and when my next drink was coming.”

It got so bad that his beloved wife considered suicide to escape the misery of their marriage.

 “Kay was at the end of her rope with me,” he writes. “I was always out, partying with my buddies, leaving her alone to raise our three sons…Kay felt her entire life was in ruins and that she had failed as a wife.”

Then one day he accused her of cheat­ing when she came home late from work.

She reveals in his book, “Phil was call­ing me every ugly word under the sun…I felt hopeless.

“I went to the bath­room and cried…It’s the only time in my life that I had suicidal thoughts …I didn’t know how to fix our lives and didn’t know what to do.”

At the age of 28, Phil says he turned his life around after rediscovering the Bible, and he went on to launch his duck caller business in 1973. He eventually parlayed that business into one of the top-rated reality shows on TV, but he may be aiming to duck out of the TV limelight.

When asked by an interviewer how much longer he plans to appear on “Duck Dynasty,” Phil replied: “Not long. But I think it’ll go on without me.”

Meanwhile, he’s found the book-writing business to be pretty simple. Amazingly, Phil spent just 10 hours speak­ing to a ghostwriter to produce his memoir.

“The next thing I knew,” he says, “somebody told me the book was No. 1 on the best-seller list.”