Hello:
Nothing is technically wrong with your sentences, but your passage would read better as:

"How are celebrity moms able to look so good just a few months after childbirth? Flipping through the tabloids, mothers who aren't famous groan, 'Some women have all the luck!'"

I dropped the "there is something really incredible" which should be avoided in writing, even for the most lightweight articles: if you can get rid of a string of words in a sentence and not lose any meaning, you should always cut, cut, cut. I eliminated the juxtaposition of "luck" and "unlucky" and replaced "looking" with "flipping" for some variety in the last sentence (because "look" is also in the previous sentence). Good luck!