I completely understand you feeling all touched out and that you're 'putting out' constantly...then again, I can't completely understand because I've just got the one 'sucker', so even in my imaginings I feel tired for you!
It's amazing what we do, when you get to the end of a day and think about the mammoth job you've just done and have been doing all this time...and that somewhere, you know you have the strength to do it again another day and a few more after that, too!
In my 'luxury' of having only one child to tend to, I can only say that I espouse 'living each day at a time', because each day comes to an end, and each day has a new beginning. One day at a time and before you know it, things will be manageable and you'll be proud of how much you've achieved within that time.
It's a hell of an input you're making, such an investment in your family. If you weaned tomorrow, make sure there's someone around in 15 year's time to remind your DS's how you loved them so much that you fed them till you just couldn't any more without compromising your wellbeing or, alternatively, till you let them decide when they were ready. Either scenario depicts a wonderful mothering effort