I've had something like that happen to me recently. I have a phobia of plastinated bodies, and ever since I heard that an exhibition of them is coming to my city I've been trying to desensitise myself to images of it (I know that I don't have to go to the exhibition itself, but there are also posters and adverts for it around the city). While doing so, my phobia seems to have developed into a strange phobia/obsession hybrid. I still feel very unnerved and a little bit sick whenever I look at the images, but at the same time I find myself looking out for them, and I can't stop talking and reading about it. Having an obsession like this is really not fun and almost feels more like an addiction, so I wish it would just go already! (At the same time, I know I can't completely stop looking at the posters or else I'll never become desensitised...)