Tenacious

Increase your Constitution score by 1, to a maximum of 20.

When you roll a Hit Die to regain hit points, the minimum number of hit points you regain from the roll equals twice your constitution modifier (minimum of 2)

Your hit point maximum increases by an amount equal to twice your level when you gain this feat. Whenever you gain a level thereafter, your hit point maximum increases by an additional 2 hit points.