Hi Laura, i have only just read this post and just wanted to say that after trying to come off Effexor a few weeks ago (had been on them for 6 months) I had these feelings also plus I had weird vibrating sensations that seemed to strat in my chest and then went through my whole body, plus I had dizziness and nausea, I couldn't cope with these feeling so went straight back on the meds and within a couple of hours the weird symptoms had vanished so I think this proves that it must be withdrawal symptoms. I find that even if I miss just one dose then these feelings come back.
I hope things get easier for you soon and congratulations on your pregnancy.
take care
Love Lisa