Volunteering work opinions?

A bit about myself i worked in a nursery for 5 years until i fell pregnant and have a nvq 2 in childcare. My daughter only goes to nursery 15 hours a week so its difficult to get work. The full day she is at school i volunteer in a nursery. When i first joined i was told even though i have a qualification i was never to be left alone with kids which is fair enough. The nursery is one big hall and a small section of staff room which has screens. One day all the staff left the room and the manager shouted from behind the screens i am here don't worry she never once looked to see what i was doing ok she is in the room but not able to see me do you think this is wrong? I also do 9.30-2.30 5 hours without being offered a drink a break nothing i have never done volunteer work or these hours is it normal not to be offered a break? I sit with the kids all day while the other staff use me to their advantage and go and do other things. But on the last 2 occasions of being there i have felt a bit of a skivvy one woman was going to sterilize the toys the manger said no get me to do it i ended up doing this for hour and a half then another woman was going to wash up and the manager said get me to do it. What im basically asking is, is this normal. I have never been a volunteer and not sure how they are treated am i being taken advantage of or not? Thank you