I'm afraid I've just had to get used to feeling pretty knackered all the time now. It's just a normal part of my existence now and I've kind of accepted that it will be for a couple more years.
That said, there are things you can do to mitigate it. I always do online supermarket shopping, an hour in the supermarket is wasted time IMO, I can usually find time during my working day to do the shop online (quite often have lists of basics saved and just add a few extra things to vary the meals)
I also meal plan a lot so I don't have to think about what we're having and I'm always sure we've got what we need in when I do the online shop. I also don't do long involved meals. I have a friend who still tries to do gourmet food all the time, but for us, we've got used to pasta I can whip up in about 15 mins (dh is a useless cook) or something similar. I've also got pretty good at doing at least one meal a week in the slow cooker (chuck everything in in the morning, hey presto, cooked meal ready in the evening!)
In terms of domestic stuff, I work long hours, 12-13 hour shifts, with an hour (at least) commute each side of that, but I only work three days a week, so I try on my days off to schedule one task per day off iyswim... ie Monday, tues, weds at work, Thurs hoovering, Friday cleaning bathroom, sat change beds, Sunday do nothing
I also rope dh in more than I used to. He's a bit useless (I think he does that on purpose so I'll take over!) but there's no reason he can't wash the kitchen floor on a Saturday morning or whatever, despite how much he moans about it.
I try and do washing overnight, chuck a load in before going to bed, and either sling it on the line in the morning if the weather's going to be ok, or hang it on the dryer in the kitchen before I go to work. I've also drastically reduced how much ironing I do... don't bother with sheets, etc, only really iron cotton shirts and anything that really needs it. Most things will do with a shake and a smooth down. Dh irons his own work shirts.
Sorry, that's an awful lot of stuff in there, but I hope some helps.
I don't want to sound nihilistic, but I do think sometimes you have to accept that being a working mother esp when your dcs are young is tiring too and the quicker you accept it, the easier it is to work within those limitations. Don't try and be superwoman, don't try to be a domestic Goddess... just get through it the best you can until the dcs can start chipping in. DS is going to be wielding a hoover as soon as he's big enough