Funnily enough I was put on mirtazapine so siphon off the effects of sertraline (heightened anxiety and tremors) and it worked, I don't get as much of the drowsiness as when I first started them and am now up to 45mg each evening. Before, when I was just on sertraline, I could have panic attacks about so much as leaving the sitting room, I even had a really bad one from so much as my partner touching my shoulder unexpectedly.

As Stella said, it can seem worse for the first few weeks once your meds are upped as your body is reacting to the increased amounts of medication, and if you're unsure of your own safety whilst taking them you should go back to the Dr and make them aware.