Priscilla Presley claims Elvis gave her powerful drugs when he was still at school, she has claimed.
The pair met when Elvis was doing military service in Germany, which he completed in March 1960 when she was still 14.
The King of Rock and Roll's former wife told how she "almost died" and was "knocked out" for the following two days after taking pills he gave her.
In an interview with Barbara Walters she told how Elvis persuaded her parents to let their daughter visit the US for a fortnight and was allowed to move permanently when she was 17.
She spent much of the days in his bed at Graceland and said The King was almost nocturnal.
Priscilla said he was always awake until almost morning and then slept through the day.
According to Priscilla she was expected to stay up with Elvis and started to take pills to help her sleep.
Priscilla explained: "I had to. Because we got home so early in the morning. He would sleep til three or four in the afternoon. He’d get his sleep. I’d be lucky if I got half an hour.
"I had to make it work. I had to do it. With the fear of a young girl fearing that if I didn’t do it, maybe someone would take my place. I always had that fear if I don’t do this, some will do it and I wanted to be the one.”
Priscilla also said she tolerated anything to keep Elvis by her side, including crazy hours and an apparent sex ban until marriage.
She told how Elvis was completely dependent on pills to get him to sleep, and "function during the day".
Priscilla added: "He had to (take them). He had a fear of insomnia. When he woke up he had a horrible fear he could never get back to sleep again."
The couple married in May and 1967 and divorced in 1973. They had one daughter, Lisa Marie Presley, who is now aged 52
Last month Priscilla broke her silence following the tragic death of her Lisa Marie's son Benjamin Keough, who died by suicide at age 27 last week.
Priscilla, 75, who was married to Elvis Presley from 1967 to 1973, penned a heartfelt statement to fans about his death via her official Facebook page.
She wrote: "Each day I wake up I pray it will get better. Then, I think of my daughter and the pain she is going through as she was a doting mother.
"Ben's father, Danny, who is completely lost, as Ben was his only son."