looks like you have a sverely decayed tooth which has become infected. you must see a dentist
who will take an x say suggest u the best treatment.
regarding the declining health of your teeth during pregnancy
, i must tell u that it is the gums which can sometimes become inflamed(or u may have a reactive lesion- pregnancy tumor/pyogenic ganulaoma over the gums) in case your dental hygiene is not good. your teeth as such will not get affected as the teeth once formed do not get affected during pregnancy other than that they may get decayed which results of poor oral hygiene
. one must see a detist during pregnancy to a an opinion on the overall health of the oral cavity.