SOLVED. YA/Teen Stream of Consciousness, narrator is insane, major shift in reality halfway

[Space]

I read this book in high school and it made a big impression on me, but I don't remember the author or title. I think the cover of the paperback was either solid blue or solid green, with a bear or a dolphin on it.

The book was a snarky/disturbing stream-of-consciousness novel where it became clear that the narrator (a boy in high-school) was insane. There were multiple scenes with an imaginary bear he kept seeing. I think he kept mentioning his ex-girlfriend who was named something like Sarah, but it was later revealed either that she didn't exist, or they had never dated, and he was insanely/violently obsessing over her.

Lots of major abrupt shifts from the narrative into flashbacks or non-sequiters, some some of which were very violent if I remember correctly.

And one thing I remember almost 100%, is that there was a reference in there to Jhumpa Lahiri. But it wasn't by Jhumpa Lahiri.

[Lobstergirl, au gratin]

What years were you in high school? Author female or male?

[Space]

I heard back from the person who lent me the book originally. it's "Eeeee Eee Eeee" by Tao Lin.

[El]

Eeeee Eee Eeee for the link