Tiffiny and her husband Ed Kavalee welcomed Vada to the world on May 30, a little sister to their four-year-old son Arnold.
After putting Vada down for a nap on Thursday, Tiffiny posted a video to Instagram detailing her struggles since giving birth while encouraging other mums to keep pushing forward.
In the teary video, Tiffiny said she had been struggling to accept her post-baby body and had been feeling "super emotional".
"I know that there are many of you out there who are pregnant or about to give birth or who have just given birth, and I just really wanted to say how important it is to bounce forward and that it's not easy," she said.
"It's not easy to bound forward and take the pressure off, even I am standing in the mirror looking at my new body, Vada's house, my big bump and it's really hard to accept that it's going to take time."
She began to wipe tears from her eyes as she spoke of Vada's birth being "painful but worth it".
"Healing takes time and it depends what birth you had... for me, I've got a few stitches and stuff's going on so it's all painful. But [Vada] is absolutely beautiful and worth it," she said.
"Arnie keeps asking me why my stomach is so big ... he keeps saying, 'Is there another baby in there mum?'. No. I'm trying to explain to him it takes a long time for bodies to go back to normal and that it's hard."
The 37-year-old urged women to be kind to themselves and not let negative thoughts take over.
Tiffiny has been praised for her candid video as other women shared their own experiences.
"Thanks for being so real and so vulnerable on this platform. Really inspiring! Take care of yourself, one day at a time and remember you gave a gift to the world," one said.
"So raw and wow did it resonate with me so much. I have been pregnant both times you've been pregnant and now have an eight-week-old," another said.
"I'll never forget what you said about bouncing back and you just wanted to enjoy your baby. I took that advice on myself and really embraced every tiny moment."
Tiffiny's latest pregnancy has inspired many, with the trainer making history as the first pregnant woman to appear on the cover of Women's Health.
“As much as there’s pressure after you have the baby to bounce back, you don’t have to have that toxic positivity mindset all the time,” she told the magazine.
“Just take that pressure off, bounce forward. Prioritise your own self-care.”
Never miss a thing. Sign up to Yahoo Lifestyle’s daily newsletter.
Or if you have a story idea, email us at email@example.com.