Pregnancy tiredness

Everyone keeps asking me lately how I'm feeling and I've been feeling great. The cramps aren't as bad this pregnancy, nausea hasn't been much at all and I haven't even been that tired....that was until today!!! Today I feel like someone came and depleted me of any possible energy in my body. My brain, my eyes and the rest of my body don't want to function at all...and I have Dallas and Asher to tend to all day. I keep eating chocolate in hope of some energy (no coke in the house :-( I think I might have to make a trip out just for some cola. I do hope this is an isolated day and that the rest of the first trimester isn't like this (for all the other three pregnancies the tiredness during the first trimester almost felt like a disease that wouldn't go away.) Anyhow...please pray for me...send me some energy!!! LOL