I am a retired RN after working 40 years. I became very burnt out on two separate occasions and, looking back. the real problem was that I was not in a role that best suited my strengths. In your instance, it does seem the best thing you could do is seek a permanent placement on a unit you really like to get some stability and be able to build supportive relationships with co-workers. And, as many others have stated, learn to say NO to those requests for OT. You must take better care of yourself in order to be at your best when on the job. Do something you really enjoy on your off time, even if it is just taking a healthy walk regularly.