If 3 other SSRI's didn't help you I don't really know if trying a SNRI is going to be much different. If you would like to try a new medication then maybe go with something different like an MAOI/RIMA , Benzo or something else (I don't have enough experiences to tell you what but there are plenty of good posts that could help you).
I personally was on Effexor XR for a couple years and while it did slightly help me after coming off I wish I would have done so earlier and tried other options.