Thanks for asking the query,
Abdominal upset can occur due to the use of antibiotics prescribed to you.
Take an antacid
half hour before meal along with the antibiotics and analgesics.
If the antibiotics are not suiting you can consult the Dentist
and get the prescription changed.
If you are having severe stomach pain it can be due to some systemic conditions i would encourage you to visit to an Gasteroenterologist and get the checkup done.
Hope this helps out.