JOHN RITTER HID DEADLY SECRET …

John Ritter ignored chest pains for a week and pushed himself to keep working — tragically mistaking his heart problem for food poisoning or heartburn.

That’s the untold story behind the “8 Simple Rules for Dating My Teenage Daughter” star’s September 11 death at age 54.

The issue that goes on sale Friday tells how Ritter’s medical drama unfolded, reveals the eerie words he spoke just hours before his death … and more.