I haven't played this game in awhile, so I started a new game.

I started out leveling up every 6 skill increases, then every 5 skill increases.

So is my game working right?

I thought it took 10 skill increases to level up.

It depends on your level and how high your skill is. On higher levels leveling is slower and getting skill from 95 to 96 contributes more than getting a skill from 15 to 16

This is one the reasons people don't level high.

Grinding becomes a necessity to level up.