New to spirits – why do they make me feel dizzy?

Probably a stupid question, but I like craft beer and am pretty new to whiskey. I know it’s like 3 or 4x as much alcohol per ounce and I only have like 1/4 as much. I’ve never been drunk before in my entire life, but why is it when I have one Old Fashioned my vision gets a little bleary and I feel dizzy/fuzzy? Does that mean I’m a lightweight or is that just a normal thing?