"I got so much scrutiny for putting on extra pounds, but I think that the decision not to make myself anorexic was actually great for branding," she explains. "Because when you're really, really skinny, not everybody can relate to you."
With a baby on the way, Simpson added that she and Johnson, 32, have yet to set a wedding date.
"I haven't started shopping for our wedding yet," she admits. "When I got engaged, everyone thought I would get married immediately, but I have not put a single dress on, and by the time this comes out I will not be married! We're just enjoying being engaged right now -- and that's honest."
Unlike her previous relationships, Simpson felt a special connection with the Yale grad. "When I met him I just felt so comfortable with myself and where I was in my life," she tells Lucky (on newsstands November 8). "If he didn't want to be a part of it, he didn't have to be."