WHITNEY HOUSTON suffered from a secret heart defect that turned her into a ticking time bomb!

A source says the tragic diva – whose death at age 48 was attributed to accidental drowning – battled a heart problem her entire life and knew she was destined to die young.

“Whitney was born pre­mature and was a very small baby,” the source revealed.

She didn’t talk about it a lot, but she knew that she had heart problems and her life was probably going to be cut short.

“So for those who knew her well, Whitney’s death was the result of an ongoing health problem. Whenever she fell ill or looked sick, we’d ask one another, ‘Is this it?’ ”

Whitney was found dead in her room at the Beverly Hilton hotel on Feb. 11, 2012. Accord­ing to the official coroner’s report, she accidentally drowned in the bathtub.

A heart incident and cocaine use were listed as contribut­ing factors in her death, along with other drugs.

But she’d often exhibited symptoms related to her heart problems, said the source.

“Some days Whitney men­tioned that she was having difficulty breathing,” re­called the source. “Other times she said that she was exhausted even if she’d just woken up. And she often sweated a lot, even when the temperature was cool.

“But she never complained. She knew nothing could be done about her heart defect, and she just kept going.”

With a death sentenced hanging over her head, Whitney decided to live life to its fullest, added the source.

“Whitney knew she could drop dead at any time,” said the source.

“Needless to say, she abused drugs. But whether or not she used drugs, she believed she’d never see her 50th birthday.

“Still, Whitney knew she was blessed, and she didn’t feel at all sorry for herself. She lived her life her way.”