Elvis Presley was all shook up and feared his music career would end when Beatlemania hit America 60 years ago.

Even though the Memphis crooner was the biggest star on the planet, he felt the Fab Four’s sensational impact could make him irrelevant.

“The King” endured “insecurity” about not appealing to youth audiences, especially as The Beatles were leading the British Invasion of the US in 1964.

Carol Connors, his secret girlfriend at the time, revealed the icon was worried his…