Is it a sign of pregnancy if your stomach hurts?

No, not really. You could have gas or have ate something that did not agree with you. Plenty of women I know that have children and when they were pregnant they said that their stomachs did not hurt but their breasts did.

Yes it can hurt, some women tend to have lower abdominal pains during their first few weeks of pregnancy and it is normal as it is goes hand in hand with breast pains too.