Cat acting strange

Hello, the cat seems to have trouble to breath or something like that...

His mouth is wide open with his tongue out and his breath is making loud noises.

I tried to give him water but he didn't wanted...

He is no longer doing that but he already did it two times today so I'm worried about him.

is he coughing and/or wheezing? if so, it could be asthma. 

He coughed two or three times but that's it.

I also noticed that his eyes were wide open and I feel like something was going on inside his stomach.

He is now sleeping but he looks very tired.

Any suggestion of open mouth breathing calls for a vet visit imo. Breathing in the way you describe is indicative of respiratory distress and needs urgent treatment.

Cats don't pant like dogs do. Any time a cat is open mouth breathing it's time to take them to the vet.