"I did" and "watching..." are separate parts of the sentence. You could equally say "... as I did while watching "Lord of the Rings"".
"Watching "Lord of the Rings"" serves a similar function as "看着LOTR" in Chinese, implying simultaneity. I'm not sure you could use this construction when translating this particular sentence into Chinese.
I think you'd say something like 看LOTR以前,我没有感过那么无聊 (literally: Before watching Lord of the Rings, I'd never felt so bored). I can't figure out how to translate it in a way more similar to the English sentence you have there.
Is it possible to say 我(别时)没有感我看着LOTR的无聊?