Feel am being ussed !?

wel basically ive just started a new au pair job in the uk were i am from.. so i came on monday at 7 had tuesday 'free' then from 5am on wensday until 3pm satrday i had a 1year 7month old an a 10 year old girl all this ime as there parent was away on a work think.. i have just been informed that i have them all day 2morow and monday so inside a week so far i have worked 80 hours or so after monday this will be around 130 hours !!! surely i sud be cled as somthing oher dan an au pair and be gettin payed more than �100 a week for these hours as the 1year an 7month old had to sleep wih me aswel so the past few days have been 24/7 :(