I'm in grad school too, and was trying to work full time... so i certainly understand where you are coming from. Honestly, the thing that has helped me most so far is allowing myself to do less. I take naps and work less and don't try to do absolutely all of the assigned reading or put the normal 110% into everything.I'm definitely an overachiever who is having to become okay with being an achiever, and you know what? So far, I only feel better physically and emotionally, so much less stress!
If your professors seem to be understanding, try asking what is most important to be read and explaining that you will get done as much as possible, but sometimes its not possible to do it all and so its good to know what to give the most weight to. My experience is they don't expect you to do everything anyways X-) Also, to help with the reading, I tend to read in really small increments of like 15 minutes at a time in a position that is most comfortable and then rest for a few minutes. It takes forever, but it also actually helps me remember more and cuts down on study time later.
I don't typically carry any of my books to class with me, but obviously with some classes you don't have a choice. You could consider sharing with somebody, going the e-reader route, or getting a cheap used/library copy to keep at school somewhere.
I hope some of that helps some...I'm currently in the process of talking to all my profs about what is going on and a few of my classmates know as well (mainly so they can drive me home if i am having an "attack") and they've all been really great so far. Of course, i'm going to school for therapy so they should be! Lol