Venlafaxine worked really well for me, for over 7 yrs. I then changed to Duloxetine after being on them only because they stopped working. The withdrawals were bad, mainly the brain zaps. But probably not as bad because i had the Duloxetine to wean onto. I don't take anything now, and it seems to have worked better for me. I wouldn't recommend it, though.
I think everyone is different, there's medication that's been named in here that I've had a horrendous experience with yet its helped others so much.
See how you are in a couple of weeks and if you are still feeling the same or you're worried, contact your Gp and raise your concerns with them. Try not to worry, although I know it's only natural and you probably are.