Shit faint - FMHY

Why is it that I almost faint if I try to shit really hsrd?

You're pushing too hard. You should breathe through it, don't hold your breath. Look into getting a step for your feet. We're designed to squat, not sit, and getting your feet higher can get things to line up better internally
Also, pushing too hard (and shitting for too long) are great ways to get hemorrhoids.