Stressed/Burn Out

Been having difficulties at work lately... Maybe I am getting a bit burned-out resulting in my temper has been really short-fused, getting a cranky easily and kind of dragging my feet to work. I feel very dis-respected and unappreciated at work as well as being 'drained' or 'squeezed' dry by my manager.
Problems faced at work include:
1) I have been working back to back weekend night duty for 3 consecutive weeks, giving myself only 1 pathetic day of rest per week. This 1 day of rest is for me to do my house-hold chores, meet up with friends and to meet my parents.
PS: I have to do frequent nights as I have few colleagues are excused from night duty due to family commitments, health reasons and those pregnant staff are automatically exempted from night duty.
2) My manager has placed me, without my consent, in some PIP (Practice Improvement Project). She just nominated my name into this project and plainly told me to take up this 'challenge' as the project leader needed a nursing staff in his project in preventing blood transfusion wastage.
3) My manager knows I can't handle morning duties as I would get 'anxiety' attacks the night before, hence rendering me unable to sleep, affecting my health and performances at work. However, she still places me few morning duties, while my other colleagues, who has excuse not to do night shift/duty gets their wishes. Do I really did to see a doctor to diagnose myself as 'anxiety disorder' just so that I am excused from morning duty?
4) My manager keeps reminding me that I am the 'Senior' of the ward based on experience and qualifications and wishes me to uphold the 'Senior' attitude when dealing with my less experienced or newer staff. Yet, when I do correct their mistakes outwardly to attempt to 'discipline' them for poor attitude at work, I am being held back by her and the staff 'escapes' the disciplinary actions or 'scolding' from me. This has led my newer or less experienced staff to walk away scot-free and they tend to lose their respect for me. I am pissed! You expect me to maintain standards as a 'Senior', yet I can't discipline when errors are being made.
5) The above event has led to me being 'disrespected' and 'ignored' at work. I even had less experienced staff telling me, "You are not even an SSN, so don't even tell me what to do, 'cause we are same rank!"
6) These few weeks, patient load has been high and the turnover rates for admissions and discharges have been high. The ward work-flow is like mad these days and everyone at work is also facing burn-out or stressed related health issues. Junior staff has been throwing MCs when they are tired out and my manager expects 'Seniors' like me and my other capable colleagues to work like mad. Then, when we suffer burn-out and fall sick, we are counselled for our high MC rates.
7) For the past 9 months, I have been voicing out my unhappiness to work shift and have requested to revert back to my office hours duties to my manager. Her reply always comes as 'No Vacancies' or 'The ward needs people like you'. However, she is sending other staffs who doesn't enjoy working office hours to temporarily fill in vacancies at my previous office hour position on a 3 months rotation. I really don't see why she can't let go of me and allow me to willing fill up this office hour position instead?

Due to all the poor management and high stressed levels, many capable staff are also thinking of resigning... Perhaps, it is time for me to move on too after July 2012, when my bond ends...