I am using this format for my section and subsection headings (it is centered and numbers have dots):
\documentclass[12pt]{article}
\usepackage[center]{titlesec}
\titlelabel{\thetitle.\quad} %dots after title number
But I cannot unbold it by using most of the unbold commands because centering changes in most of them. Is there way to unbold the section and subsection headings with this format?

\titleformatcommand to set the format of the section heading. – Werner May 14 '14 at 22:53\sectiontitle (and chapter etc) – Werner May 14 '14 at 22:55