I can understand your concern for abdominal pain
in your girl friend after unprotected sex.
The details of the concern are quite less to reach to any conclusive point as we want to know the last date of menses along with time period of unprotected sex on a particular date after menses.
In general if unprotected sex is done from 10th to 17th day of last menses then are quite unsafe and can result in pregnancy
. so you count your days accordingly.
The best would be to go for home test of urine sample for pregnancy.
If she is taking Krimson 35
regularly as prescribed then three are negligible chance of pregnancy but if in irregular fashion then can be a problem.
Abdominal pain and vomiting can be a sign of multiple internal abdominal problems for which you must see a doctor.