Have you tried a dildo up your ass? Trust me, if you use a large one it IS painful at first but then you start craving it. Just that and the clothespins on my nipples will sometimes make me cum. Of course, what you're fantasizing about at the time will also have an effect.

Another possibility is using a messenger and cam to have someone tell you what to do to inflict the pain on yourself and watching you obey.

Good luck!