I've only taken (1) celexa that my doc prescribed to me for panic...

I've only taken (1) celexa that my doc prescribed to me for panic disorder and I already feel exhausted. I had the worst panic attack I have ever had after 30 minutes of taking it. I started yawning like crazy, I became very spaced out and had to go to the bathroom. I had way more energy when I woke up this morning. I'm not taking another one. I called my local nutrition store. They had good suggestions. I'll go see what my alternatives are...something more natural.