Recurring allergic rhinitis that flares back up as soon as a short course stops is common in pregnancy, and it usually means the treatment needs a review rather than a repeat of the same short course.
Next Steps
Go back to your gynaecologist and mention that the same short course isn't holding, since a longer or different pregnancy-safe plan may suit you better.
Health Tips
The chills and loss of appetite with your flares are worth flagging too, so your doctor can rule out anything beyond allergy alone.