Anyone else exhausted??

So I've been pretty active through my pregnancy. I've gained more weight than I'd like, but it hasn't stopped me from going to the gym and running a few miles and lifting weights 3 times a week or so. But for the past few days, I am just wiped out! My husband and I took our dogs to a dog festival this morning, and afterwards I basically napped for 5 hours.... Anyone else experience this???