Healing Curse

You gain an ongoing  and developing cursed ability to heal yourself while forgoing  any other healing magic/items.  Talk with your DM on flavor and how it'll work 

As an Action you  can heal 1d10 damage per level, and minus 1d4 psychic damage per level + your con modifier.  Once per long rest 

At level 5 you gain the ability to do half of the healing/damage role  as a bonus action. Once per long rest

Level 10 you get another action of full healing and using your level instead of con modifier. 

Level 15 you get another bonus action  healing. 

If in the middle of combat roll a Con Save (14 bonus action, 17 full action) or be stunned for a round.  At level 20 you can forgo this requirement. 

You gain the benefits of a ring of regeneration (1d6 healing for every ten minutes) and every healing item/spell/food item etc either doesn't work or hurts you per the Dm's descretion.