Jen, I'd vote for a doctor visit too, just to rule out everything. Could even be an ear infection. They could also probably give you some ideas, if it's not something physical, on how to get her sleeping pattern straightened out.
I know it's hard sometimes, I had four kids, in eight years, with the middle two 15 months apart. Looking back, I have no idea how I did it. lol!!
Does your mom, or other family member live near, so they could watch them while you took a nap?
Hang in there, this too shall pass. But I think I would start with the doctor visit.
:-)