You have enhanced physical stamina.
Benefit: You gain +3 hit points. For every Hit Die you possess beyond 3, you gain an additional +1 hit point. If you have more than 3 Hit Dice, you gain +1 hit points whenever you gain a Hit Die (such as when you gain a level).
Pathfinder RPG Core Rulebook. Copyright 2009, Paizo Publishing, LLC; Author: Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook, and Skip Williams.