If you can at least tolerate your job, you should go back. What you are feeling in part is probably because you've been gone so long. I had a meltdown and spent three months out of work and in treatment. I also had your feelings at the thought of going back. Had to face it. It got easier after a day or so. Then it was like I never left. If you are full-time now, see if you can do your first week back part-time. Also, try going back in the middle of your work week so you don't have to do the first whole week.
I'm no expert, but you probably just need to face the demon and get the first day back over with and behind you. Believe me, nothing's changed and you'll probably be fine by lunch the first day.
Hope that helps!!!!