I could ask you the same thing.

[It's a bit of a stall. Part of her wants to keep trying to hide what's happening, but she knows she can't hide it much longer. Especially not with someone she lives with. There isn't much time left unless she figures something out. She pauses for a moment, inwardly arguing with herself, before settling on a toned-down version of the truth.]

I'm... well, I'm afraid I'm not feeling all that well. It should pass, soon enough. It usually does.