I want to stop masturbating. Therefore I swore (Thursday morning) for that I would not do that for one week. After that I made this fault again on Wednesday. Please advise me how to get rid of it. Do I have to make "Sawm" for three days?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Know, dear brother, that masturbation is forbidden. See Fatwa: 81150.
However, we advise you to (1) avoid exciting things such as songs, films and pictures; (2) to keep busy with what is good and beneficial; (3) to associate with good friends; and (4) to be above trivialities and elevate your way of thinking. More advice you will find in the above-named Fatwa.
As a final word, you have to make expiation for a vow.
This expiation is as follows:
1) Feeding ten poor people on a scale of what you feed your own family.
2) Or: clothing them.
3) Or: freeing a slave.
If one cannot do any of the above choices, then he can fast for three days.
More information in our Fatwa: 82841.
Allah knows best.