I used to feel exactly like you about Facebook. I would check it
constantly, so much so that when I cmd+t'ing to open a new tab I would often instinctively type "f+return" to have Chrome open the site.
45 days or so ago, I deactivated my Facebook account. If you're not familiar, this allows you to "pause" your account -- nobody can access your profile or interact with you on the site while deactivated, but once you log back in, your account instantly resumes where you left off.
It took a week or so to overcome the Pavlovian urges I had developed from years of habitual Facebook additction (albeit often for intellectually stimulating and/or social causes).
The bottom line was this: I've been loving every minute of it since. I feel more free and less tethered to my phone and computer. I have more down time and I find myself less stressed out and, frankly, feeling better about myself.
Oh, and one more thing, lest you assume (perhaps reasonably) I didn't have much doing on my Facebook account anyway: I'm a high school senior. Facebook is huge at my school, and a lot of fun grade/school-wide gossip/interaction/planning happens there. And you know what? I'm president of the student body and if it's important, people can tell me in person.