Actually,i do think those answers to this question make sense in a way, but i won't recommend you to use them, because those are not that verbal and not that exact,but those did suggest the meaning you wanted to convey to some extent.and you'd better use them in written Chinese, but as far as i can see,the sentence you gave us as an example sounds more oral,so i would translate it this way:
我从没想过背着你做些什么,你知道我一向都是按你说的去做的。
(BTW according to your explanation to Petter, you said going behind one's back is more related to action. so i do think this is pretty good a way to say,considering colloquialism and generality.)
So generally speaking, we say "going behind your back" in chinese like: 背着你做些什么,背着你干些什么。
For instance:
他总是背着我干些偷鸡摸狗的勾当。
别以为我不知道你成天背着我干些什么!
And actually i think there's also another way to say it in chinese, but i do not recommend you to use it, because it's a bit like slang in English if we have in Chinese, ;p 别耍花样.it also means don't try to go behind my back, but in a more threatening way.for example:我警告你,别想再耍什么花样!
Hope this helps, just keep asking me if you still don;t get it. ;p