Well, while I can't give you an exact piece of 'Jackson gets Stiles pregnant' fanfiction, when looking on fanfiction platforms, make sure to read the summaries and reviews. This will help you filter out the stories that might not be what you're looking for. Also, some platforms have a rating system, so if you prefer a certain type of story in terms of tone and content, you can use that to narrow down your search.
One possible plot development could be the initial shock and confusion for both Jackson and Stiles. They would have to deal with the unexpected situation, especially considering the implications in the context of their relationship and the world they live in (assuming it's set in a particular fictional universe).
One interesting aspect could be how their relationship evolves in the context of this unexpected pregnancy. Maybe they start to communicate more deeply and understand each other on a new level. For example, Derek might become more protective of Stiles, and Stiles could discover a newfound strength within himself as he prepares to become a parent.
Often, these stories also focus on the emotional journey of the characters. There could be feelings of fear, excitement, and love all mixed together. The pregnancy can act as a catalyst for a deeper exploration of the characters' emotions and their bond with each other.
Fanfiction.net is also a great place to look. Just use the search function and type in 'Peter gets Stiles pregnant'. However, the quality and content can vary widely, so you might need to sift through a few stories to find what you like.
Well, often in these fanfictions, Stiles becomes more confident. His physical appearance might also change, like he could start dressing better or have a new haircut that gives him a 'hot' look. For example, he might start wearing more stylish clothes that show off his personality.
Writing about underage characters getting pregnant is inappropriate and goes against the spirit of the original 'Percy Jackson' series which is mainly aimed at a younger audience. So, there should not be any such fanfiction in an appropriate context.
There could be. Fanfiction is a vast world, and the 'Jackson is Stiles' baby concept might have been explored by many authors. However, the quality can vary greatly. It depends on what you're looking for in a story, whether it's fluff, angst, or something else. You might have to sift through a few to find one that really grabs you.
Often, it shows Stiles growing in maturity. He has to think about more than just himself now. And Derek might become more empathetic as he's involved in this very human experience of pregnancy.