My period came on July 12,2012 I had unprotected sex July 18, 19, 20 2012 am I pregnant? Is there a chance

There is a chance. Any time you have sex there's a chance of pregnancy.

Are you? There's no way for us to be able to give you that information, we'd need either your urine or your blood in order to determine pregnancy, and this early on that wouldn't even give us answers.

Wait until our period is due. If you miss it test a week later. If that test is negative wait another week or two and test again, or wait until the next period is due and if you miss that test or see a doctor for a more accurate blood test.