It's quite obvious your addiction is the major problem. In your post you even already mention your escapes : 'can internet at work' (and on smartphone and at friends and offline at home). Others here tell you, and other others even also say internet can no longer be socially avoided. It's like telephone has been for 100 years, TV for 50 etc.
Now, my advise from here would be addiction control. Yes, the AA will tell alcoholics to entirely quit. Such hardly ever works. Any cigarette smoker will tell you the same. Smoke 1 cigarette after 5 years of quitting, and you'r hooked up again. Also, again, as others point out: internet is an essential part of modern society, and as such even its addiction needs special treatment.
My [patent pending] proposal for most addicts is: Addiction control. Quit the idea of quitting altogether, as a regular thc, ethanol and nicotine user i can guarantuee you such idea is prone to fail. It comes down to some self-discipline and yes, technology makes it easy. It can help you, morally.
Chances are you have a modern router. Find 'parental settings' or something, and set a time clock. Of course, you can overrule it (and from an addictive point of view i even say: feel free so, to do so, at any time you wish). But the netto effect is: If you do nothing (have this self discipline) your internet will be on between 19:00 and 20:00, enough to check your email after cooking, and shuts down after. In the morning dito, have a 30 minute timeframe to fetch that mail or facebook.
On older routers, just plug in such simple 24h wall-clock.
Also, leave pc on, purposely, to rediscover the stuff we could do with computers for 30+ years (about since home computer was invented, around 80's) without ever using internet. Yes, the good old cassette tapes etc, maybe you have nostalgia to that times? [personally, nostalgia, yes. longing back to it, no. how convenient 'just clicking download' is these days]. Going off-topic here, cause my key point was: it's about addiction control:
Make appointments with yourself. Try to keep to them. Do NOT feel guilty when you don't keep to them, just review the appointments you made with yourself.
gl from a junkie.