Minecraft sensitivity is weird?

I'm playing minecraft on pc and when I move my mouse up or down the sensitivity is lower. How do I fix this?

It has nothing to do with lagg btw

Go into the options and change the d*mn sensitivity

You can't, you're mouse moves as a percentage of pixels of the total top to bottom or left to right side. Because monitors are wider than they are tall, mouses move faster going side to side than up and down.