Best advice i could give you is to occupy that free time with other activities that stimulate your brain in a positive way; read books, go out, solve crucigrams, listen to music, WHATEVER, just stay on movement.
At least in my experience, I've found out that using the internet properly is more helpful than leaving it completely, but your case might be completely different.
I mainly use the internet to navigate bandcamp, lainchan, this forum and youtube, with an extension that gets rid of the feed, and i try to limit my usage per day so that i don't get isolated overtime, and so that i get stuff done.
Just try to leave the internet for some time and see if you star to feel any better after a week.
Good luck.