Coming off duloxetine after four years..

I'm washing out duloxetine after a while of taking it - its just not working anymore. I'm being switched onto venlafaxine as I have chronic pain and although duloxetine is said to work well for this - it hasnt for me even at 120mg a day. The withdrawal is horrible and I'm trying my best to get through it.
Has anyone taken venlafaxine to help with pain? I am getting to the point of hopelessness and really sad/tearful all the time. I'm also trying exercise and have bought a cross-trainer but its so hard even doing 30mins on this when you feel so bad/are hurting.
JB