brake and tail light switch bad? on 1995 Cadillac Seville STS

I have a 95 sts and now my brake lights wont work on drivers side. the tail light also flashes at times and the turn signal doesnt work on this side. we have already replaced the bulb but still no fix. could this be a switch? any suggestions?

Asked by for the 1995 Cadillac Seville STS
its a switch under the dash its round that plugs in closest to thedriver side door
check the wireing under the left trunk lid hinge,thats why my 1998 cadillac sts stopped working on the left side only(under rear deck).