Thanks for trying to help. I'm not sure if that's the cause. This weekend was pretty busy, with people around to celebrate my sister's birthday. My sister is home on the weekends, and I try harder to act happy around her so as not to worry her.
Also, I need weekends to catch up on sleep and rest. I can barely manage the week - let alone if I'd actually have to do something in the weekends too (besides cooking, which I've been doing every weekend for the past couple of weeks. And studying, of course). Honestly, trying to add things to my weekend schedule sounds scary. I can't imagine how it would fit.