Human nature makes us inflict discomfort on ourselves.
In the same way that your tongue prods a dental cavity even though you know it hurts, so we allow ourselves to scratch open the itches of healing wounds - so don't beat yourself up over it.
That said, it is not good for you, and you need to try and remove all the temptations if you can - staying away from any Facebook entries that may give you info. is a good move.
Of course its tempting to know that the relationship he ditched you for is in trouble - you would not be human if you didn't take some pleasure in that, but ultimately, this is not helping you to get past this difficult time.
Make sure your time is filled as productively as posible - time with friends fills the gap you have left, and you will get past this, and it will take some time, but you can help the healing process by keeping your emotional tongue out of the painful cavity, which takes discipline, but pays off in the long run.
Getting over someone who has cheated on you takes time - rebuilding your battered self-confidence is a painful process, but you are getting there. Stay strong.