Why I am always thirsty..
And what's mean that?

Check your blood sugar. Excessive thirst is a symptom of diabetes.

I have to agree with OG, have you had your blood sugar tested recently?

I have had check out the rate of my sugar by almost 3 years ago
Everything was OK
Now I do not know
Perhaps I must check out again

Are you urinating a lot also?

Yes, you should have it checked out again if you are continuously thirsty.

I am always thirsty as well and I urinate all the time. However, blood sugar is just the beginning on what needs to be tested. I have MS (No to say that is what you have, there are many more symptoms to MS than that) and urinating a lot is part of it and being thirsty could be a reaction to medication as well. You could have a urinary trac infection as well. I would talk to my doctor again.