Usually a doctor starts you on a low dose for a few weeks, and then increases it. Have you seen doctor since the original prescription was given to you? You are on a low dosage, and will probably need to increase it.
I found, also, that on the generic form of Effexor, I did not do so well. I do believe there is a difference. Cost may make a difference to you though. I have Venlafaxine (Effexor) a good anti-depressant.
Go talk to your doctor and tell him how you feel.
Let us know how you get on.
I would suggest you talk to your doctor about this, it sounds like you might need to increse you dosage
It's likely you may need a small dosage increase, that's pretty common. You're on a pretty low dose, so you have lots of room to go up. Discuss how you're feeling with your doctor and see if he/she recommends bumping you up a bit.
Let us know!