11:33 AM PT — A rep for Dog tells us, "I can confirm Dog is under doctor's care and is resting comfortably. Thank you for all of your well wishes – keep 'em coming."
11:16 AM PT — Our sources now say Dog suffered a possible heart attack, but doctors are performing tests to know the precise nature of the problem.
Sources tell TMZ the reality TV star was taken to a hospital from his home in Colorado after feeling a pain in his chest.
They're also trying to figure out if he will need a corrective surgery.
Either way … it's a scary incident for the Chapman family coming just a few months after Beth died from cancer.
Beth's death has been incredibly hard on Dog — he broke down in tears at her Colorado memorial — who's also been dealing with other forms of stress lately.
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