Work place is taking the P***

So i work in a convinence store. The shop is open every day 6am-10pm. I am contracted 16hours n do a mix of 10-2/2-6 or 6/10pm shifts. but lately seem to be doing every 6-10pm shift. This week my manager is expexcting me to do 4 in a row and even snuck an extra one in without asking me bringn me over my hours. Its really starting to pee me off. Im 24wks pregnant and starting to feel it now. Also my cars broke so means i have ti walk 40mins there and 40mins back. Ball ache getting buses as beed to get 2 diff ones. And why should i pay taxi fare when there putting me in all these shifts. Annoying thing is the manager lives above the shop n puts herself in all the day shifts. Is there anyway i stand here? As me and another woman was meant to do 2days and 2 eveing shifts that we were happy with but were always stuck with the lates 😡