phentermine and antidepressants

I'm wondering if anyone else on antidepressants finds that phentermine seems to counteract the antidepressants?  I have been on antidepressants of some form for 10 years.  I currently take Cymbalta and have for over a year and a half.  Before that its was Lexapro, Celexa, Wellbutrin, Prozac.  Seems I've taken everything except Paxil, Zoloft, or Effexor.  I find that after a couple of years the antidepressant doesn't seem to be as effective anymore and i have to change.

I used to be really thin, I'm 5'10 and weighed in the 120s until I started antidepressants.  The weight gain has been so gradual over the past 10 years that it has crept up on me and I now weigh 190 (all time high was 204).  This is AFTER I had 4 liters of fat sucked off me earlier this year.  I've been taking phentermine (doctor prescribed) for about 3 weeks and have lost 6 pounds, but I have had the MAJOR BLUES for no particular reason and just yesterday it dawned on me that maybe the phentermine is counteracting the Cymbalta.  Anyone else experience this?

Just wanted to tell you I also gained weight on Cymbalta....20 pounds in the 3 months I had to wean off of it.  Just what a depressed woman needs....weight gain! :)  Anyway, I don't know if the phentermine is affecting it, but it did cease to help me and just left me flat after about 9 months.  take care!