My health does not regenerate.

I have tried eating and waiting once i am full for my health to regenerate again, it didn't. I have tried dying to reset my health, and it still didn't regenerate. The only way I have figured out to bring up my hearts again is to sleep in peaceful mode, as i wake up with full hearts. Otherwise nothing seems to work. I have also tried deleting Minecraft from my PC and re-downloading it twice, nothing has changed as well.