I would like to know why while I brush my tongue I feel like i`m just about to puke?

Gag reflex. Many people, unfortunately, cannot brush their tongue without gagging. If you are one of those, take some steps to eliminate the gag reflex when you brush your tongue. Use a toothbrush with soft bristles. Harder bristles can be more abrasive on the tongue and trigger your gag reflex. Stick your tongue out as far as you can when brushing it. Stretching the tongue out can help to eliminate gagging.
Gag reflex. The back of the tongue is inner aged by the 9th and 10th cranial nves, which make up the gag reflex. This is the contraction of your throat muscles that is involved in vomiting, and touching the back of the throat can stimulate this contraction, with or without actually causing you to throw up.