Hi.. Can understand your concern.. As per your complain pain and soreness in mouth can be due to wearing of the new retainers as initial adjustment phase is going on and any new hard thing placed against soft tissues can cause its irritation and soreness. In case of irritation caused due to soreness Numbing gels like Oragel can be applied. Pain under the jaw and difficulty in swelling can be due to infection in throat leading to inflammation of the tonsils leading to enlargement of the tonsils and pain in swallowing.. I would suggest you to consult your dentist back and get a check-up done and in case if it is due to throat infection you should consult a physician and get evaluated that whether it is bacterial or viral infection.. In case of bacterial infection antibiotics can be relieving.. In case of viral infection anti viral medicines are not taken as they do not provide relief.. For both bacterial and viral infection few treatments can be: Do warm saline gargles. Throat lozenges can be sootheing.. In case of pain Ibuprofen can be taken as it helps in relieving pain and inflammation.. Sip on luke warm water throughout the day to maintain hydration ans relieving the throat.. Avoid hard and spicy food... Take a soft and nutritious diet.. Hope this information helps.. If you find the answer helpful please write a positive review and click on find this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.