There are only two basic answers to the question "You aren't hungry, are you?" : they are "Yes, I am."
or "No, I'm not."
Similarly, if your mother said, "You are hungry, aren't you?", the two possible answers would also be "Yes, I am" or "No, I'm not".
As you can see, the Yes/No word is in accordance with the statement it accompanies.
If you say "Yes", this usually accompanies a positive statement. For example, "Yes, I can", "Yes, you do", "Yes, they have", "Yes, it is" and so on.
Likewise, if you say "No", this generally accompanies a negative statement. For example, "No, I can't", "No you don't", and so on.
In English, it is not normal to follow "No" with a positive statement. Responding to your mother's question by saying "No, I am" would sound very strange to an English speaker.
Here's the problem. I think you are interpreting the words "Yes" and "No" as being the same as equivalent utterances in your own language. I suspect that you want to say "No, I am" because ( in your mind) the word "No" means "No, mother, your statement is not correct" and then you go on to explain that you are actually hungry.
Unfortunately, that isn't how it works in English. In English, the 'No' or 'Yes' at the beginning of the answer has nothing to do with whether or not the question was phrased in a positive or negative way. Whether you say 'Yes' or 'No' depends on whether the statement which YOU are making is positive or negative.
I hope that makes sense.