Heidi Montag got her breast implants reduced in size because they were causing her severe pain.

The former 'The Hills' star, who shocked her fans after she underwent 10 plastic surgery procedures in one day in 2010, recently went under the knife again to have her implants reduced from a size F to a size C, because they were causing her back problems.

She decided to have six-hours of surgery on October 4 after reconstructive specialist Dr. Jay Orringer warned her that her chest was ''bottoming out''.

She added: ''He told me they were falling through the bottom, and I got scared. It's super dangerous. They can fall through to your belly button!''

The 27-year-old model also told Us Weekly magazine that she grew to hate the size of her chest.

She said: ''I couldn't conceptualise the weight of them in my body. They felt like bowling balls on my chest.''

Heidi, who is married to her former co-star Spencer Pratt, was also suffering a number of health problems, including neck pain and numbness in her arms, related to the size of her second set implants, which weighed ''about three pounds each.''

The blonde beauty, who first boosted her chest to a C-cup in 2007, is thrilled with her new figure.

She said: ''I'm the new, new, new Heidi!

''Now my spine doesn't hurt and my neck feels better. It's like I can breath for the first time in years. I am just more comfortable in my skin. And I can wear cuter, tighter shirts. I don't even have to wear a bra!''