The word »selber« is a synonym for »selbst« if the english word »self« is what you mean.
Ich kann das selbst. = Ich kann das selber.
I can do it myself.
But be careful! »Selbst« has a second meaning, that can be translated as »even« in English. There is also a German synonym for this meaning, it is »sogar«:
Das kann selbst ein kleines Kind. = Das kann sogar ein kleines Kind.
Even a little child can do it.
This means »to feel sorry« or »to feel pity«, but its usage is different from the English usage:
Du tust mir leid.
I feel sorry/pity for you.
In English the person who feels sorry is the subject, but in German this person is the dative object. The person that you feel sorry for is an object in English, but in German it is the subject. So in German, it is the person who you feel sorry for, who is the source of the feeling, and the person that has this feeling is the person who receives this feeling. (Da-tiv = the giving- and receiving-case. The latin verb "do, das, dare" = to give.)
But you can also feel sorry about yourself:
Ich tue mir selbst/selber leid.
I feel sorry/pity about myself.
So, the translation of the complete sentence is:
Könntest du aufhören, dir selber leid zu tun?
Could you (please) stop feeling sorry/pity about yourself?