AceShowbiz - Singer Cassie's battle with postpartum thyroiditis meant she "didn't even recognise" herself after gaining 60lbs during pregnancy.

The star and her husband Alex Fine welcomed daughter Frankie in December (19) and the 33-year-old "Me & You" singer revealed in a recent blog post titled "What Healthy Looks Like to Me" that it took her a while to snap back into shape after welcoming her little girl.

Explaining the weight gain "had many negative physical effects" on her body, Cassie explained, "I lost 20lbs within the first couple of weeks which I was told was normal and then another 10 gradually over the next 2-3 weeks."

"I started to workout when I had a goal of 30lbs to go and when my doctor cleared me to. I went pretty hard at first," she shared. "By mid March I was down another 15 and feeling pretty good. I had a bit of unexplained anxiety, but I was able to work through it and down another 15 meant I only had 15lbs to go to get back to my pre-baby weight."

However, Cassie said the weight loss "only lasted a couple of weeks" and she gained 15lbs back, prompting her to undergo bloodwork that eventually led to her diagnosis.

"The next 3 months following were confusing and depressing to say the least," the hitmaker continued. "I changed my diet paying attention to things that I reacted negatively to (ie, bloating). I actually started roughly following an autoimmune diet (AIP) in fear that my thyroiditis would turn into Hashimoto's Disease (an autoimmune disorder)."

After finally "understanding" what was happening to her body, Cassie credited her fitness trainer husband for helping her to stay focused "because he wanted me to be happy again."

"Today I'm in better shape than I was before the baby. I honestly don't think I've ever been in this good of shape," the new mum wrote. "Whatever your goals are, choose to be healthy. For me, this is what it looks like when I'm taking care of myself. This is what healthy looks like for me."