I'm sorry that you are having such a hard time with school right now, but you've got to stick with it. I just graduated in May with a B.S. in Communications and I remember being very overwhelmed and I'm young with no kids and I didn't have Lucy yet, so I can only imagine what you are going through.
Here are some studying tips that might help:
I used to always re-write my notes out before an exam or test, I would also answer any questions that were at the end of textbook chapters.
If you are having trouble reading and remembering I always found that reading out loud helped a lot. Also taking notes on anything important from the text, might also be useful.
I know you said you can't get any peace and are distracted, have you thought of maybe going to the library?
Good luck and hang in there
