If your wife has missed her period and the home pregnancy test is positive then she is already 4 weeks pregnant. Please calculate weeks from the first day of last period. Mild pain is normal in pregnancy but if the pain is unbearable then please consult your gynecologist. Dehydration causes pain so ask her to drink plenty of water.

Little pain is fine . As it happens due to implantation. Wait for sometime then you can visit your doctor if it's bothering you. Give warm milk and ask her to rest ..