Effexor XR to Celexa?

I have panic disorder, not depression, and a slight case of social anxiety. Effexor XR has done wonders for me, seeing as though I haven't had a panic attack since taking it (along with lorazepam, which is mostly for withdrawal, slowly getting off of it). I have had slight insomnia from it but feel as though as long as I exercise for twice as long I will get over it. My psychologist prescribed me to Celexa and I've heard bad things about it, but good things as well. Anybody else switched like this? (Info: he wants me to take it at night, I drink alcohol often which is why I like Effexor b/c I take when I wake up) Effexor has helped me so much I guess I'm just scared to switch to another drug which could bring back panic attacks..experiences would be helpful..thank you