SOLVED. Middle Grade Fantasyish novel about a depressed boy who accidentally shrinks his sister and makes everybody disappear. read during lockdown i believe. colorful cover with an outline of the boy. [s]

[sincerelynne]

The boy was 11-14 years old, his name might have been Mikey but that could be completely wrong. His sisters name might have been Sara. He and his sister have kind of a rough relationship and the sister has a boyfriend who's a jerk and bullied the boy. I think he likes drawing. His parents are divorced, and I think both of them are gay and dating/married to someone else but it might have just been one of the parents. His dad is the gym teacher at his school and the boy was like refusing to participate. One day he woke up and everybody was gone. I don't think he was at his house anymore either -- he might've been in a desert? But then he found his sister, and she was small enough to fit in his pocket. I also vaguely remember something about him turning invisible.
Minor spoilers ahead!
If I remember correctly, he was like inside his drawings? That might be wrong though. The big villain he had to face at the end was like a different/evil version of himself. They made it back home somehow and he and his sister ended up friends again and she broke up with her boyfriend, one of the reasons being "he used gay as a slur." After the experience he was generally much happier.
That's all I can remember, I hope it's not too vague!

[Rainbowheart]

The Incredible Magic of Being?

[sincerelynne]

No, unfortunately that’s not it. Thank you though!

[Becca]

The Anti-Book by Raphael Simon looks like a match

[sincerelynne]

Yes that’s the one! Thanks so much