It's confusing whether you're referring to the entropy of the universe or the entropy of your body. Fisrt of all, even if you could 'travel through time' this would not prevent biological effects from happening so even if you were immortal your cells would eventually stop reproducing and die.
Assuming this is magically prevented, there are solutions to Einstein's field equations that would allow for time to 'flow backwards' in which case there would be no problem with you going back in time to a hospitable point in time and reliving it over and over again.
Entropy always increases, it's the 2nd law of thermodynamics, but that doesn't mean that an object put into a system will immediatley reach equilibrium and no longer have the same characteristics. Eventually it'll reach equilibrium but something as structured as a human wouldn't suddenly cease to exist to conserve entropic equilibrium. It's all a matter of whether you choose to go back in time and exist in an environment that wouldn't destroy your body, like a star or vacuum would.