It's pretty common as the addiction escalates. People look for more and more forbidden things or engage in more and more extreme behavior in order to get the same level of thrill as they used to get with more vanilla stimuli. I haven't gone this direction myself, but I know lots of instances of straight men seeking out gay images (or vice versa).
I'm sure that in no way reduces the pain or causes the behavior really to make sense, of course.
By chance today I ran across an article discussing the neuroscience of this exact phenomenon. I have no idea how accurate the science here is, but it at least seems to me to describe what many people experience. Here's a link: