Kristin Cavallari says motherhood has changed her ''in so many ways for the better.''

The 28-year-old shoe designer, who has two sons, Camden, three, and Jaxon, 17 months, with NFL star husband Jay Cutler, says she owes ''so much to [her] babies'' and can't believe she is going to give birth to their third child soon.

The former 'The Hills' star, who is set to welcome a baby girl next month, posted a black and white photograph of her baby bump on Instagram, with the caption: ''It's hard to believe I will be a mom of three in just a few short weeks. I owe so much to my babies... they have changed me in so many ways for the better.''

The blonde beauty is also gearing up to release her memoir 'Balancing in Heels' next March and admits she found the writing process very emotional.

She added: ''I talk about my journey to mommy-hood, my pregnancies, and how these little guys have made me who I am today in 'Balancing in Heels'. The mommy and wife chapters are incredibly raw and real - I don't sugarcoat anything.''

Kristin previously revealed 'Chicago Bears' quarterback Jay is unlikely to be there when she gives birth to their daughter because he is scheduled to have an away game.

She said: ''My mom will be there. Hopefully it will be easy [and] I'll be in and out.

''If he's not there it will be unfortunate, but I don't think I can say, 'Babe, you can't go to Green Bay or wherever you're going to be, I need you home with me.' But it's fine, it is what it is.''