Is she pregnant or fat?

Judging by the "plump" tag, I'm guessing fat.

Well her arms are thin so I think that she's pregnant

Not necessarily, Etna. I've got a belly similar to hers, I'm not pregnant, and my arms are pretty thin.

Can I make a request for more of these? Fat Miku is nice.

I'm too lazy to translate the whole thing at the moment, but the gist of it is, her Master is congratulating her on a good workout, but she's thinking how much she hates exercise, and the way being sweaty makes her skin feel, yet she knows that after exercise comes "massage time" and she doesn't want to miss out on that.

is she bleeding?

from the looks of it it's bad colored sweat, as it is only in the shadowed areas