The breath of life focuses on the growth a creature can obtain and constantly changes a user by using breathing. 

First Breath

Starting at 3rd level, you "die" in your next long rest (this doesn't count towards affects that rely on death) and you are born anew and cannot be knocked prone any more even when knocked unconscious 

New Day, New You.

At 6th level, you change and can pick from: Heart, Lungs, Bones, Skin, and Muscle. These are perminate unless the class is removed.

Heart: If you get affected by the blind, deafen, paralyze, or poison conditions then their durations are halfed.

Lungs: You can hold you breath by 3 times your consitution modifier (if you have the Hold Breath ability then this is additional instead of overiding) When you drown you stay consious but will still fail death saving throws until you are able to breathe.

Bones: You have 1 Damage reduction against all physical damage and have advantage on checks that have to do with balance.

Skin: You have 1 Damage reduction against all magical damage except psychic and the effects of extreme cold/heat are treated as if you are resistant to it.

Muscle: Athletics has expertise and you can add dex and str score to your jumps.

Body

Choose 1.

Heart: If you get affected by the blind, deafen, paralyze, or poison conditions then their durations are halfed.

Lungs: You can hold you breath by 3 times your consitution modifier (if you have the Hold Breath ability then this is additional instead of overiding) When you drown you stay consious but will still fail death saving throws until you are able to breathe.

Bones: You have 1 Damage reduction against all physical damage and have advantage on checks that have to do with balance.

Skin: You have 1 Damage reduction against all magical damage except psychic and the effects of extreme cold/heat are treated as if you are resistant to it.

Muscle: Athletics has expertise and you can add dex and str score to your jumps.

Joy of Life

You understand important the ups and downs of life is and are able to harness that energy in you as a technique.

You can use The Living: as an action you harness the energy of every living creature in that combat and use it to effect the area within 500ft of you in these ways. (you count the amount at the start of combat)

5 living: The ground is difficult terrian for you enemies.

10 living: Your enemies are tripped unless then make an dex saving throw vs. your monk DC.

20 living: All enemies on the ground take 12d4 damage

30 living: Enemies on the ground that fail a Str save vs. your monk DC can't take reactions for 1d6 rounds.

50 living: can revive an ally as if you used the revivify spell (does not need components).

The Living only restarts at a new combat and you do not gain extra points if a new creature enters combat. 

Last Breath

At 17th level, after you down a opponent you can choose to give your opponent an -1 on death saving throws (if they are able to make them) when getting a 20 on the roll they just get two successes and a 2 on a roll counts as a nat 1.

Any creature you killed you can use 8 ki points to absorb their experiences and power, when you make an melee attack you do you martial arts die of damage to enemies in 10ft of them, when an enemy is knocked out this way it does twice your martial art die damage to enemies 10ft of the person downed.