Trade against

is it posible that if i sell some currency at some price the broker that i work whith will ofer some other clients to buy at that price,so the price will go up.
or if i buy some currency at some price the broker that i work whith will ofer other clients to sell at that price so the price go down?
i hope i explaind my self
i meen if the broker that i work with can make the oposit trade,as i open a position,if i sell he buy and if i buy he sell,and in that two cases i loss

the broker is not playing against you. he is more or less like a middleman. he will take a buy from you and sell to me.