I am super belatedly making the rounds on all the fic I've been storing up, and dropping by to say how much I love every sentence of this for offering reasons, real reasons, even if they're still hurtful and don't make sense. "This can be like drinking" is perfect. The "if Kurt calls me..." game, and the fact that he rejects it = It doesn't matter, so much, exactly what Blaine does inside that house. What matters is that he goes there, and things start, and he stays.
As much as I like everyone's more detailed speculating, that right there is the only summary we need.