You probably skipped some of the side quests, which is making you slightly underleveled. As long as you're not struggling, don't worry about it too much.
On the other hand, if you are having a lot of trouble finishing battles, it wouldn't hurt to go back and finish up a few of those side quests so your health increases. Also, leveling up can get you into better gear with more accuracy. Accuracy and damage both improve a lot as we level up.