I had sex three times on september 6 my bofriend cum in me four times my perood is suppose to start september 11, 12, or 13. what is my possibility of becoming pregnantone week away from my period?

Probably low: If you are having a period each month, then you would have ovulated about a week before you had sex on sept 6. The likelihood of you conceiving is almost zero. If your periods are irregular, then you could ovulate almost any time and the chance of conceiving would be higher.

Very possible : Consider taking Plan B which is available over the counter and decreases the risk when taken within 72 hours. Then see your doctor to start effective birth control.