I had my last periods on 27th July 2012. How many weeks I am pregnant? I have pain in lower abdomen is it dangerous?

Don't mean to be rude or too personal but it depends when you had sex. You would have become pregnant within 72 hours (3 days) of it so just do the maths.

Oh and some abdominal discomfort is normal but if it is really bad and persistent you should see a doctor

Have you actually confirmed a pregnancy with a test?

Don't mean to be rude or too personal but it depends when you had sex. You would have become pregnant within 72 hours (3 days) of it so just do the maths.

Just plain wrong. Pregnancy is dated by the LMP (Last Monthly Period), not by when a person has sex. It takes 3-5 days for the sperm to reach the egg after intercourse, and then another 3-5 days for the implanted egg to reach the uterus.

You most likely conceived ( assuming you are pregnant and it is confirmed) after the last period, and before the next due date. So that gives you a estimated 4 week window.

Latter the doctor will give you a estimated date, that should be good within about a 2 week period. Unless you just had sex once in that time, an exact date is not possible

Have you actually confirmed a pregnancy with a test?

Yes