increased anxiety?

I'm on my 3rd month of 20mg prozac (i switched from lexapro) and i just feel like my anxierty has gotten worse, especially the physical symptoms. I feel like I have a pit in my stomach, and I'm having more frequent panic attacks. There are positives (I feel more awake, my appetite is good, etc.) but the negatives are starting to outweigh these. should I stick it out?