Hi Chris... I am sorry to hear about the ups and downs that you are experiencing.
When starting on an anti-depressant, some individuals can see a pretty immediate decrease in their anxiety/panic attacks/depression symptoms, others see a steady, gradual improvement, and some show an up and down pattern. Mine was more of an up and down pattern, similar to what you have described.
I am not certain when you started on the Zoloft, but anti-depressants do take time to work. Normally, individuals will see degrees of improvement between 3 and 12 weeks of being on a therapeutic dose. And, you do have some room there to increase the Zoloft. An acquaintance of mine is on 200 mg, and doing quite well on that dosage. Finding an anti-depressant that works best for you, is indeed a case of trial and error. What works well for you, might not work at all for me, and vise versa.
Lara gave you some sound advise. One usually stands a better chance of seeing improvement, when medication is taken in conjunction with therapy. Other forms of treatment known to work include exercise, and the use of omega 3/fish oil. A healthy lifestyle is also of benefit. This can include keeping oneself hydrated (drinking plenty of water), eating frequent, small meals, and practicing meditation and/or mindfulness.
The very best to you, Chris!... Chuck