08/27/2008 at 07:00 PM EDT
Happier personally and professionally than she's been in a long time, Jessica Simpson
tells PEOPLE that boyfriend Tony Romo is her "perfect guy."
"I just told him today, 'You're the love of my life,' " she confesses in the latest cover story. "I don't really ever say that to anybody."
Simpson, 28 (as is Dallas Cowboys quarterback Romo), also co-wrote a song for her man, "You're My Sunday," which is featured on her new country album, Do You Know
(out Sept. 9). And, in a true modern-day sign of devotion, changed her cell phone number and e-mail address to cut off any potential communication from her exes.
"I don't want anybody that's been in my life [before] in my life anymore," she says. "I don't even want them to have any way of contacting me."
Romo hasn't done the same, but Simpson brushes it off. "I'm not a jealous girlfriend," she says – even though in a recent interview his ex, Carrie Underwood
, claims she still hears from him.
As for her own onetime relationship with John Mayer
– which began in 2006 and fizzled out last summer – Simpson survived its rockiness by doing some self-appraisal afterwards.
"I had to regain self-esteem and self-value," she says.
When it comes to relationships, Simpson says she gives over her heart fully and expects the same in return: "I just love, so I don't understand when people can't do exactly what I do."
For the complete story on Jessica Simpson and Tony Romo – including why she needs a secure man in her life and her hopes for kids and a family – pick up this week's PEOPLE, on newsstands Friday