Why am i getting charged a different amount every month?

how do i check what i am being billed for? I get billed a different amount every month,the only thing I have is apple music for $9.99 yet I am being charged $12-20 every month for apps I dont even have? Where can I see what I am paying for to stop getting charged this much,I do not want to pay anymore then $9.99 a month for the apple music and that is it!