Jessie James Decker is getting real about her struggle to lose weight after giving birth to her third child, son Forrest, last March.

On Tuesday, the 30-year-old country singer shared before and after post-pregnancy pics on Instagram, showing off her noticeable weight loss. In the before pic, Decker takes a selfie as she hits the gym, and in the after pic, she looks fitter than ever in a pink bikini.

Decker, who credits her weight loss to following the South Beach Diet -- which emphasizes eating high-fiber, low-glycemic carbohydrates, unsaturated fats and lean protein -- admits she struggled with her body changes after giving birth.

"I know you’ll see a lot of people in the public eye and they drop weight in what seems like five minutes after having a baby and I think we all feel like we should live up to those expectations," she writes.

"I’ve even been guilty of that myself and thinking I need to rush and lose weight two months after having a baby when I see all these skinny girls post baby but that is just not realistic for the majority of us. I have been every shape and size over the last 4 1/2 years from having children and never had to worry about losing weight until I had kids. I had good metabolism and had always been that way before."

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"Having children definitely changed everything and I’m so blessed and grateful to have my babies as y’all know but it definitely can test your self-esteem when you are used to looking and feeling a certain way," she continues. "I got up to 165 pounds with my first baby and being 5’1 it was really hard on my frame and I definitely struggled self esteem wise."

These days, Decker says her goal is to be happy and healthy, not just "skinny."

"Don’t ever feel like you hit a dead end road or you want to give up or feel hopeless," she tells her followers. " ... I even have provided a before and after shot. I’m a little nervous about showing y’all that before because I was pretty uncomfortable but I want to keep it real with you guys!"

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This isn't the first time Decker has gotten real about her post-baby body. In January 2017, she embraced her "loose mommy skin" in a bikini on Instagram. Aside from Forrest, the singer is also a mom to 4-year-old daughter Vivienne and 3-year-old son Eric.