<human>: This started a long time ago, as far as I can remember.

My tongue goes through an awful sensation every time I drink water, which seem to contain various chemicals, such as chlorine.

I presume it's the chemical content of the water as the faster I drink the water the worse my tongue is affected. It is hard to explain because it is not a sensation of pain, but one of **great discomfort**. It also feels as if the tongue's surface is being saturated with the chemicals present in the water.
Not all waters cause this, mostly tap water and occasionally bottled water. Some brands of bottled water don't cause this, I make sure I drink those.
Water drunk mixed with coffee and/or milk doesn't seem to cause the same sensation, I presume that this is because the water's chemicals become saturated and don't interact with the surface of the tongue the same way.

I've been to various doctors around Europe a while ago, but nobody has yet managed to find out what it is. I guess it is also because of the inability of explaining what it feels like with precision. 
It would be really great if somebody could tell me what this is! And if there is any way to treat this.

Summarize the given text in a few sentences.
<bot>: I can't drink most tap and bottled waters affect, my tongue seems to not like the chemical content of it. I have no clue why this is...