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."

"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!"

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. 

ET spoke to Decker and her husband, former NFL star Eric Decker, last October, when they shared a surprising -- and kind of gross -- fact about their marriage. Watch the video below for more:

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