3 points of intel everytime I want to learn a spell?

[Osky Re]

I started learning spell normally but as time progresses it tellsme I needto raise my intelligence to learn new spell. I add 1 point of intel and nothing happens so I had to raise it 3 points which allowed me to learn 1 extra spell not more than 1. And it is like tis every time.I have several scrolls with spells in my backpack and can'slearn them because of intelligence, which by the way is in 31 or something like that.
Am I doing something wrong? Or it is the way the game is meant to be?

PS the same happens with wisdom and the divination spells.