I was reading a story recently that may have been from the glee angst meme but I don't think it was completed. Kurt was at Dalton but was struggling to fit in, I think he was reluctant to let Blaine know how uncomfortable he still was. From what I recall Kurt became ill, like with a cold or flu and it got to the point where he wasn't able to eat without throwing the food back up and spent a lot of time in the bathroom feeling ill. Because he felt so isolated from the Warblers he didn't tell anyone what was going on and finally he passed out during a Warblers practice session. When the nurse comes in asking questions, Blaine and the others realise for Kurt's situation to get so bad he must of been ill for some time and none of them had noticed - cue guilty Warblers. I don't think Kurt and Blaine were together but Kurt did have feelings for Blaine. That was as far as I'd gotten and after some very frustrating attempts to find the story which I could have sworn I'd bookmarked somehow I am desperately asking for help!
Mods: Hopefully the tags are correct but as I'm uncertain about a couple of aspects of the story I'm not 100% on the genre but I'll correct if need be if the story can be found.