Without more information, I'm inclined to say it's your hormones.
You're a SAHM so don't have work to contend with. Granted you have a toddler so it's a little different. But there's many of us here who've worked until 8.5 months pregnant and still managed to do laundry.
I'm due in a week and yesterday I did two loads of laundry, vacuumed the house, and ironed and folded all of the baby's vests and baby grows and put them away in to drawers ready for his arrival.
This isn't a one off. Granted DP may do extra cooking (but that's not just because I'm pregnant, he's the better cook), but we both pull our weight with housework. He does the harder stuff, lifting, scrubbing the bathroom etc., but we both work full time (I only finished last week) and share the chores.
Whilst I've been off this week, I've done the cleaning whilst he's been at work so when he gets home, we both rest.
Yes, I'm a little tired, but not so much that I cannot do anything in the entire 8 hours that I'd usually be at work.