Boku ni Natta Watashi

Welcome to Momoko's waking nightmare. Things were settled. They were! She was SUPPOSED to have gone to a normal school, made normal friends, and led a blissfully normal life. But the universe is just cruelly, irredeemably, monstrously unfair, so instead she found herself thrown out of home, stuck in an all-boys boarding school with a roommate she hates, cursed with a hideous haircut and wearing clothes which, to be frank, she wouldn't be seen dead in.

And the only thing worse than her current situation is the one that she'll be in if anyone ever realizes that she is, in fact, a girl. Everything is wrong! Everything! Particularly the fact that, even though she's surrounded by amazingly gorgeous guys, her chances of romance are less than zero. But with life this complicated, something is bound to give. In fact, it just did. Damn.

(Source: Storm in Heaven)

Included one-shots:
Volume 2: Nopan Musume. (A Girl Without Panties)
Volume 3: Aah! Ijuin-sama
Volume 5: Kimochi Henkousen), Massugu na Kanojo