Dietary changes

I've been thinking lately that i might have some kind of gluten intolerance and was wandering if anyone had advice on testing or past experience with avoiding gluten, what symptoms they had before etc.

For the past year also I have had some considerably mood changes, I feel depressed (feeling of dread, just down about things, bad outlook on life) which is something i never felt before and was always an upbeat person.
I get nervous about many more things that usual, social situations become increasingly more frightening, and I am increasingly uncomfortable around people.
I also feel quite tired and get irritable, and take offense to things that people say and read into their motives far too much, making me hold grudges. One minute ill think someone is my friend the next i question whether they really are etc.
I also have a constant fog in my brain, i can't concentrate on what people are saying, i find it difficult to find the write words, become forgetful and disinterested in activities due to the constant thoughts in my mind.

Physically i have terrible smelling gas and stools (which often float and look kind of grim, dont really know how else to describe them). I also have shallowing breathing and poor circulation to my hands and feet and often get pins and needles in the extremities. I'm fairly skinny (6 foot tall around 65/70 kilos) and have hardly any fat on me.
I look much older than 20 years old (hair loss doesn't help hah) and have dark circles under my eyes.


Thats the main things that i have noticed and i'm sure i must be doing something wrong with my diet to be feeling this way. If anyone has any input i would be very grateful, I would like to get some testing done but don't what to ask for here in the u.k...

Thanks