However I acknowledge it may be harder if you're in between: trying to control yourself but having it crucial to your job. As hard as t may be, I could only recommend my own strategy: trying to organize your time properly, and stick to it.
This doesn't imply that people who are addicted to social media actually have OCD, rather that social media is a sort of supernormal stimulus for "checkability", in the same class as slot machines and chocolate chip cookies. Regardless, it should suggest the hypothesis that SSRIs, which help eliminate the compulsions of OCD, might also reduce the Internet-based compulsions the negative impact the lives of normal people. Anecdotally, taking SSRIs has helped my Internet addiction immensely, though the usual caveats of n=1 studies apply.
Like car doors and ovens, there's rarely any marginal benefit from checking Facebook fifty times a day instead of twice a day, or at least no benefit that outweighs the opportunity cost of constant checking. It's a slot machine that you play with attention instead of money, which is just as bad if you assign any reasonable financial value to your time.
Repetitive Facebook checking is supposedly more like an addiction - people are chasing the endorphin rush that comes with finding a new message (or winning at the table) rather than trying to chase away anxiety.
Page also contains links to other useful apps. I really like Spirited Away.
After rereading the post, maybe not applicable if the sites are crucial to get work done.
For increasing productivity, use pomodoro or similiar simple/simpler techniques. Its all about creating a habit.