Hi thanks for your question.
you are 38 weeks pregnant and have vaginal swelling for which your Doctor given you a prescription.
you have not mentioned what does prescription cantain ?Has he prescribed you any medicine.
The vaginal swelling is most probably a vaginal infection
or an infected bartholine cyst
,which are normally present in vaginal wall and get enlged in infection.Since your 38 week pregnant ,it is better for you to reconsult the Doctor rather than taking the antibiotics.
Hope this answers your question.