Fatigue is pretty much the most common side effect from Paxil, at least that's what my doctor advised me of. I've been on Paxil for about 1 week and 3 days now for SAD (10mg/day for a week, then 20mg a day), and initially I did notice I felt exhausted much more easily and was practically falling asleep in my classes. It also made my anxiety/palpitations much worse initially, and I had to increase my Klonopin doseage. The fatigue is much better now though, but I just got a sinus infection so I can't really notice a change in my anxiety yet

. My anxiety always acts up when I get sick.
SSRI's have different effects on everyone, and if you are experiencing normal side effects they usually won't last more than 1-2 weeks. If you still feel fatigued after 3-4 weeks I'd try something else.