"I'm 102 lbs. but my belly's not flat anymore and it's never going to be, and I'm okay with that," the singer tells PEOPLE

Credit: Kimberly Henderson

Mother of four Kimberly Henderson was tired of feeling like she had to hide her post-childbirth stomach, so she decided to bare her belly – loose skin, stretch marks and all – in a candid Facebook post that has since gone viral.

“I’ve always been super insecure about my post-baby body,” Henderson, 27, tells PEOPLE. “I’m 102 lbs. but my belly’s not flat anymore and it’s never going to be, and I’m okay with that. I posted the picture because a lot of people see me and they’re like, ‘Your body’s so perfect, how’d you have four kids?’ I’m like, ‘If you only knew what’s underneath these clothes!’ ”

The South Carolina-based singer hoped her post would help other mothers feel more comfortable in their own skin.

“I wanted other moms that felt like I did in the past to not worry about it, and embrace it, and just be confident with who you are,” she says. “Stretch marks and loose skin – that doesn’t matter. I wanted them to be able to say, ‘I have that same stomach, and I can still wear my bikini.’ If you feel confident and beautiful in your skin, then that’s going to be sexy to anybody.”

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Henderson – who is currently working on new music – worried that because of her small frame, people would criticize her for sharing the photo, but fortunately the responses have been overwhelmingly positive.

“I didn’t want people to get the wrong idea or think that I was complaining,” she explains. “I was just worried that what I wanted to get across wasn’t going to get across, but it actually did. I’ve gotten negative [comments], but the positive definitely outshines the negative. Everyone was moms just like me, and that’s what I wanted.”

Henderson’s post currently has over 100,000 likes and 10,000 shares.

“Honestly I was shocked because when I uploaded it, I had no idea that it was going to blow up the way it did,” she says. “I always felt alone. I would always be the one hiding behind the one-piece. I had no idea that there were so many people out there just like me, because you see so many perfect stomachs on Facebook and you see so many celebrities walking on the beach that are so perfect.”

Not only has her post inspired others – commenters have posted that she gave them confidence to wear a bikini again – but her post has actually helped Henderson with her own self-image.

“Reading the comments made me feel better about myself because I’m like, ‘Wow she’s beautiful and she’s 105 lbs. and her stomach’s just like mine!’ ”