I neralt blacked out during my workout?

I have been doib the p90x workout for about 2 n a half weeks n today early durin my workout my vision got real blurry n early blackout I took a good break n continued quickly after I started again I nearly passed out again startin to feel dizzy n vision kinda blacked, all this was followed by sky rocketing heartbeat which normally doesent happen, I drank a red bull about 15mins prior to my workout which I never do, my diet is not that great even poor if that n I dnt dring much water, what r some suggestions? Could I have a heart problem, or is it my diet? Should I dis continue this workout?