My pregnancy conspiracy theory: I think the positive test belongs to Wendy.
It technically could still be any of the side girls, since presumably some or most of them hook up with other characters throughout the story, but the things we know for sure are:
- It can't be the MC's (unless the person in question is Zoey), because you don't have to have sex with any other character in the game, and
- It actually can't be any of the main girls either: Jill is a virgin, Maya has never been with a guy, Isabella hasn't been with anybody in years, and the only people Sage and Josy cheat with are the MC, but since you don't have to hook up with either of them, it can't actually be them, either. (Technically it could be Sage's, but the odds are incredibly low based on her conversation with Chad about how they never have sex.)
Having said that, I don't think it's likely that it would be any of the side girls, though, as depending on your playthrough, they may not play that big of a role in the story. Sure, you might like Riona as a character, but someone else may have barely interacted with her at all, which means the revelation that she's pregnant would lose a lot of potential tension. The only potential exception to this is Quinn since she's more significant to the story regardless of the choices you make in the game.
Assuming that it's in the present and it's someone at B&R, I think it's most likely that it's someone one of the Diks hooked up with, because they all have ties to the MC. That said, I don't think it's likely to be Elena, Arieth or Dany. While the Diks are interesting characters, Rusty, Tommy and Derek are each significantly more important to the story than the other five. Again, it's fine to like the characters, but the other Diks are more bit players and so a potential pregnancy related to them would have less of an impact.
I think Heather is reasonably likely since Tommy plays a bigger role in the story, but I still think the most likely character is Wendy. My reasoning:
- No matter what decisions you make throughout the game, Derek is the most important character to the MC other than his dad. He's your bro, he supports you through everything, and he's been there since almost minute one. Anything involving him just has more emotional weight than it would with other characters.
- IIRC, the only character Derek absolutely hooks up with is Wendy. I think there are scenarios where he doesn't tag-team Arieth with Jacob, and obviously Lydia is determinant on whether you tell him about Jade. Even if he does hook up with Arieth, though...
- If Derek does have sex with Lydia, he specifically references that there won't be a pregnancy scare with her. It could just be him making a quip about a horrible situation, but...
- In gender studies, Wendy specifically tells the MC that Derek thought she was pregnant. But more importantly, she also says that "I may only had sex three times in my life, but it's basic knowledge that you dont't get pregnant that fast." (the typos are actually in the game)
This tells me that she is by far the least likely sexually active character to have used any contraceptives, and in fact she might not have even understood the possibility that she could become pregnant. It's easy to imagine her telling Derek that she wouldn't get pregnant, and it's also easy to imagine Derek just hearing that and going back to just ignoring her. It could also explain why she's so hung up on Derek in general.
