Thanks for your query.
and benadryl are safe in pregnancy but cetrizine
safety is not sure during pregnancy,so benadryl is more advisable than cetrizine during pregnancy.
Yes post nasal drip
and nasal congestion
increase during pregnancy because of increase level of estrogen hormone but you don't worry.
You are already taking amoxicillin and benadryl,please take plenty of fluids orally,steam inhalation and vitamin C.