Maribel, Hi and hold on there. I would advise you at this point to beleive strongly in yourself and continue to do only your best due to the circumstances. There is only so much you can get done and that's that on that. Most times staffing knows it is not fair to you, as well as the DON and administrator.
Your best bet, might be to look for a job that entails a lighter work load, therefore when you are short staffed you might not feel as overwhelmed.
Also, I would suggest trying the Hospitals because the patient load there from my experience is entirely better! You will most likely have fewer patients on each shift offered at hospitals. Assisted Living places are a bit better; however I would not highly reccomend these due to the possible decrease in pay.
You might want to run an ad in the paper to find yourself a "private duty case" this way you can screen your client as well as the pay you desire. If you like flexibility, you might like to sign up with atleast a few home-health agencies (Always sign up with more than 1 home agency at a time though...to guarantee yourself more desired work) unless you find an agency that has bundles of CNA cases available.
You might even consider furthering your schooling...Ofcourse, with this only you know what is most feasible for you to do. Whatever, you should decide just know that there are more job options out there and you do not have to be entitled to this for of employee's abuse ("work of 2 people").
In order to do better you will have to initiate some form of ACTION. Set goals and plans to increase a bit of happiness for yourself; After-all don't you deserve it? So you might want to consider this advice on your next off day.
Best of luck,