You don't have a disorder. You have weak attention, and very low willpower.
It's like being fat and unfit - the best way to fix it is to exercise your mind.
Make a conscious effort to cut out one distracting behaviour at a time, and start meditating to build your attention up.
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Man the fuck up and get shit done. If it's becoming as bad as you say, setup a hosts file and put all the sites you 'waste time on' on it and tell yourself you won't remove the sites from the hosts file until you get X done.