I'm right there with you. Currently looking at a kitchen full of dirty dishes & trying to think of something to eat that won't be much effort (Looks like frozen waffles). Anyway, I'm constantly tired these days with no motivation to do anything. Which is rough seeing I have a 2-yr-old to "entertain". I find that forcing myself to get out of the house helps a bit. If I'm around the house, I've been doing things in chunks. So yesterday I folded the laundry, then relaxed on the couch for a bit. Then I took it up and put it away, straightened up the room, took a shower, and then rested on the bed for a bit. Then got up an vacuumed... you get the idea. I didn't get as much done as I'd hoped, but at least it was something.
I don't remember being this tired with DS, but I was teaching PE classes at the time (leading yoga) and working with our school's athletes, so I might just have been too busy to really deal with the fatigue. I was also 2 years younger (but still no spring chicken). This year I'm staying home, which I think allows me to dwell on my miserableness more. I've been forcing myself to go out to playdates at least twice a week. I'd love to force myself to the gym, but that's not happening yet.
As for diet, I finally printed off the checklist on Dr. Brewer's site & posted it on my fridge in a plastic pocket. I'm checking off the nutrients that I eat each day to try to keep me on better track. It's not perfect, but it does remind me to eat and to eat a variety of things, especially since veggies & protein are not on the top of my list right now. It's not perfect, but I'm doing better than I was (making better choices). You might consider adding a B6 & B12 supplement to you diet (or make sure you're getting a lot of foods containing them) to see if it helps with the energy.
In the end, remember that it's OK to be tired during this part (and really all of it) and you need to take care of you. Listen to what your body is telling you that it needs and try not to beat yourself up for the slacker days. Set a goal for each day and try to achieve that, but let the rest slide. I know that I'm not SuperMom (at least not yet), and I'm OK with it.
Hope you feel better soon. Hope we all do, for that matter. Hang in there