There is a site that mocks all the FML postings (and the FML site).
Typical posts go something like this:
My central A/C got too cold, and my fresh espresso wasn’t 140 degrees when I first sipped it. And the stainless steel fridge was so bright in the sun through the skylights that I couldn’t see the TV in the kitchen this morning, so I drank from the wrong travel mug before heading out to the mall! FML.
I can’t find the darn site. FML/ 
Seriously… what’s the URL?!
There are a few sites like that whose names are all some variant of “first world problems”.
Edit: Although none of the ones that I just looked at explicitly have FML at the end of posts, so maybe you’re thinking of something different.
Sounds like #richpeopleproblems on Twitter
FML stands for Fuck My Life, and the site the OP is looking for is fmylife.com.
That’s the original site, the OP is trying to find a site that mocks that one.
MyLifeIsAverage is full of Harry Potter, Pokemon and Dr. Who nerds.