hopeful,
i had a similar situation. even on this board, some said that my obsessing and thinking was me- but i can tell you that as much as i tried, it actually was beyond my ability.
taking medication really helped- the one im on is for OCD and not only does it make the sticky thoughts less sticky, it really helps me to get him out of my head. just sometihng to consider. ive been in counseling for years, and working on our post breakup for about 8 months and i pretty much thought of it every waking second. i have made a ot of progress- still ha ve sooooo far to go.
i am having trouble moving on too, and the best way as mentioned, is no contact. i am sorry you have to see him. i dont have any suggestions there but if you find something that works, let me know- and ill do the same.