Say you have sex on a Monday, how long after will you know your pregnant?

I had sex with someone last Monday an the comdom broke. Yesterday she called and said she went to the doctor because she was having some stomache issues. She called me and told me that the doctor told her that she was pregnant. Is that a long enough time to to tell if your pregnant. Now before she went to the doctor, two days after we had sex, she said that she had gotten her period. an someone answer this for me.