It's quite possible that there is such a fanfiction. Fanfiction thrives on exploring different relationships and storylines that may not be part of the original canon. Given the popularity of the characters Lucy and Sting, some fans might have been inspired to write a story where Lucy is pregnant with Sting's child. You could also try reaching out to fellow fans on social media platforms dedicated to the relevant fandom to ask if they've come across such a fanfiction.
In Sting x Lucy x Gray fanfiction, a frequent theme is power and how they combine their powers. For example, Sting's dragon slayer magic, Lucy's celestial spirit magic, and Gray's ice - make magic could be combined in unique ways to overcome challenges. Also, loyalty is a big theme. They are loyal to each other and their guilds, and this loyalty is often tested in the stories. There are also themes related to self - discovery, as each character might learn more about themselves through their interactions with the other two.
The pregnancy in the fanfiction can be a turning point in their relationship. They'll have to face new responsibilities together. Sting might become more serious and responsible, which Lucy will appreciate. And Lucy's vulnerability during pregnancy will make Sting more protective. They'll also have to make sacrifices for each other and the baby. For instance, they might have to cut down on their individual adventures to focus on their family, which will show their commitment to each other and the new life they're bringing into the world.
Well, a plot could revolve around Sting being overly protective of Lucy during her pregnancy. He might try to keep her from going on any dangerous missions, which could lead to some cute arguments between them. Then there's the idea of them preparing a nursery together. They could have different ideas about how it should look, like Sting wanting it to be all about Sabertooth's colors and Lucy having a more whimsical design in mind. And of course, there could be a plot where they discover that their baby has some special magic abilities even before it's born.
Lucy might become more protective and maternal. Since she has always been kind - hearted, her pregnancy could enhance her nurturing side. She would likely be more cautious about getting involved in dangerous battles and focus more on the safety of her unborn child. Sting, on the other hand, might become more responsible. As a dragon slayer, he is used to being carefree, but with a baby on the way, he would start thinking more about the future and providing for his family.
One plot idea could be that Lucy and Sting discover they are pregnant around the same time. They could then support each other through the various challenges of pregnancy in a magical world. Maybe they have to deal with magical side - effects on their unborn children due to their own powerful magic.
Yes, there are some out there. You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. However, the 'lemon' aspect might make it a bit more difficult to find as some sites have restrictions on explicit content. You may need to search specifically for 'Fairy Tail Lucy x Sting romance' if you don't want the more adult - themed stories.
I'm not sure if there is a specific 'lucy x sting' fanfic rated M. You could try searching on popular fanfic websites, but make sure to follow their terms and conditions.
One great place to find Sting x Lucy x Gray fanfiction is Archive of Our Own (AO3). There are many stories there with different plotlines. Some might focus on adventures where the three of them team up against a powerful enemy. Another option could be Fanfiction.net, though the quality can vary more. You might have to search through a few pages to find the really good ones.
One common theme is friendship. Many fanfictions explore how Lucy and Sting become friends and support each other. For instance, they might help each other out in battles or deal with personal problems.