You do not draw your power from worship of a Deity. Instead your magic was drawn out in life through an emotional event, anywhere from fear while being brought to the brink of death on a battlefield to grief over the loss of a loved one. Whatever this catalyst was you became a magnet for the powers of one of the planes that make up the known universe: the Positive Energy Plane. 

The Positive Energy Plane is made up almost entirely of positive energy, the force that empowers all living beings. Positive energy manifests as a white, glowing surge of power and is used to heal creatures or harm undead, existing as the antithesis to the negative energy that empowers undead and harms the living. While such energy can usually only be wielded by adept magic users or divine servants you can harness this magic as if it is second nature, often by channeling the emotion(s) felt during the event that gave you such powers. 

Inner Strength

This domain does not grant domain spells. Instead, you gain the ability to harness your own inner strength. You gain an additional cleric hit dice. This increases to 2 at 5th level, 3 at 11th level, and 4 at 17th level. These hit dice do not alter your maximum hit points and you regain all of these expended hit dice after a long rest. 

In addition you do not use a standard holy symbol. Instead, your spell focus is an item that holds great significance to you, such as the necklace of a loved one or a wedding ring. 

Ablaze

Whenever you fail a saving throw or miss with an attack roll you can expend one of your cleric hit dice and add it to the roll, potentially turning it into a success (roll a d8 + your constitution modifier and add it to the roll). If this would cause a saving throw to succeed you can deal radiant damage to the creature that forced you to make the save and if it causes an attack roll to succeed the attack deals additional radiant damage to the target. This radiant damage is equal to your cleric level and ignores resistance and immunity.

Well of Life

Also at 1st level your existence acts as a conduit for the positive energy plane. When you heal a creature with a spell or feature you can restore hit points to another creature of your choice equal to double your proficiency bonus. The second creature must be within 30 feet of you and you must be able to see or hear them.

You can use this feature a number of times equal to your Wisdom modifier (a minimum of once). You regain all expended uses when you finish a long rest.

Channel Divinity: Frenzy

Starting at 2nd level, you can use your Channel Divinity to draw out the strongest emotions of creatures around you.

As an action, you present your holy symbol, and each creature of your choice that can see or hear you within 30 feet of you must succeed on a Charisma saving throw (a creature can choose to fail this saving throw) or have their strongest emotions overwhelm them, whether for good or for ill. You can choose one of the following effects, choosing an effect for each creature of your choice:

-You end an effect on the creature causing them to be charmed or frightened

-You charm or frighten the creature for one minute

-You make the creature indifferent or hostile to another creature of your choice for one minute (the latter effect only functions if being hostile to the other creature would seem like a reasonable course of action. Two close adventurers who have saved each other's lives would likely not be affected but a troll that sees a goblin being incompetent during the fight could be compelled to attack that goblin and make it a nice snack)

At the end of each of its turns, a creature still under one of this this feature's effects can make another Charisma saving throw. On a success, the effect ends on that creature. 

Spark of Life

Starting at 6th level, whenever an ally is about to fall you can expend your own energy to save them. When a creature you can see or hear within 30 feet of you would be reduced to 0 hit points you can use your reaction to expend a hit dice. The chosen creature is instead reduced to 1 hit point and the creature that would have reduced them to 0 hit points takes damage as if you activated your 'Ablaze' feature. 

Potent Spellcasting

Starting at 8th level, you add your Wisdom modifier to the damage you deal with any cleric cantrip.

Fiery Retribution

At 17th level, your healing can also inflict retribution on creatures. When you heal a creature with a spell or feature you can also deal radiant damage equal to double your proficiency bonus to the last creature that inflicted damage to the target creature. This damage ignores resistance and immunity. A creature can only be dealt this damage once per turn.