Anti-anxiety medication

Is it possible for my Zoloft not to be working after surgery?  Does anyone have any suggestions?  I have been a moody pill lately.  Could be that I'm reading those damned "Twilight" books and I can't stop crying about them.  Sad, I know.  But I wondered if the 50 mg pill was enough now? Or if it has time to work it's magic.  Has anyone had any similar problems with medication.  I am not normally sad, I'm usually just irritated very easily.

Thanks for any insight!
Lisa

I have not had zoloft post op but no issues with xanax or wellbutrin.  

Zoloft like wellbutrin stays in the system for a while (longer acting).  Maybe absorption is incomplete? Or maybe it is what you're reading.  (Avid reader here.  What is a "Twilight" book.  )

Sometimes we just get resistant  to a dosage and need an adjustment. 

I have not had my surgery yet.  But, I have heard at support group meetings to expect mood changes during the first few weeks post op, maybe longer.  Apparently, our estrogen levels change drastically during the rapid weight loss.  It has something to do with estrogen being stored in our fat cells.