I and my gf get petting a week ago with underwear on it (each of us). is there is a possibility that my gf become pregnant since now my gf get stomach ill?

Pregnancy is not possible in above circumstances. Contraception remains otherwise key in avoiding undesired pregnancy and associated anxiety and when intercourse is likely to occur. She should seek medical attention for her symptoms.

It takes the introduction of fertile sperm into the vagina to lead to pregnancy. What you mean by petting is not clear. If no sperm were injected into the vagina the symptoms are not from pregnancy. Pregnancy related symptoms would be triggered by the same hormones that turn a test positive. If concerned, do a urine pregnancy test.