I've been on Wellbutrin SR 150 mg (twice daily) for more than a year now. It's miraculous for me, no doubt. But similar to your experience, my level of anxiety was going up after taking it in the first month or so. My doctor then added Doxepin 10 mg to reduce the anxiety. He told me to take Doxepin twice daily. I tried, but then I became too tired. He then told me just to take Doxepin once daily, in combo with the Wellbutrin (twice daily). The combo seems to be working very well. My anxiety level rarely goes wild anymore. When it does, however, my doctor suggestion is just to take Doxepin twice daily again. When the anxiety goes down, I can decrease the Doxepin back to once daily.
Please don't give up on finding the perfect medicine for you. I've tried Zoloft, Prozac, Lexapro, Effexor, etc., but only Wellbutrin (and Doxepin) really work for me. It did took me a while to find the correct medicine and the process was indeed painful and frustrating everytime I had to go through the negative side effects before the medication kicked in. But it's really worth trying. My life is getting back to normal now, no more extreme withdrawal from people, no more extreme suicidal thoughts. There is so much life beyond depression. Best of luck to you!