Quitting is a bit of a horrible word isn't it!? It has expectations attached and those can make our decisions to leave or change field quite difficult sometimes.
I am in a similar boat. I will leave my PhD...I think :-)
I don't enjoy the work and don't see how this is going to change any time soon. I don't really feel too bad about leaving...conflicted about disappointing people, but less so about leaving in and of itself.
Here's the good news - there are always other and new opportunities. There are more PhDs out there too. In the grand scheme of things, the only thing that matters is that you did what you loved.
So my advice is this: if you love the discipline you're in and you want to continue within that field, try to speak to advisors, get help from counselling and take some leave and then come back to your PhD.
If you're not in love with your subject or discipline, leave. You won't regret it and feel relieved you do.

I think I've fallen out of love with my PhD...heck the entire psychological discipline. I'm really not enjoying it and thinking about changing back to a previous career field. I came into science from a different background, did incredibly well in my master and got onto a good PhD. Said PhD however requires me to commute between London and Leicester and will require me to commute considerably more soon. I've sort of been given an ultimatum by my supervisor now as she knows I'm not moving and won't commute too much, but for her the distance thing isn't working as well, all of which I can understand and am not criticising. Commuting of course is also time-consuming and expensive. My PI has been ok with me working from home since a lot of what I do is computational and dry research, but now she's changed her mind. Even though I think I could agree on just one day a week, I have a feeling she will change her mind about that and require me to commute more often soon. Then there's the issue of the second year, which will require some lab work...
I made a dumb decision taking this PhD. I am now painfully aware of that as I'd hate to disappoint her, myself and my parents. I am pretty sure I will leave it as I'm not particularly concerned about not finding another one. Sometimes things just don't work out...