well probably best to consult a doc. but that's the same effect I ever got from SSRIs. Incredible insomnia from both prozac and zoloft and even natural things that raise serotonin, i get anxious racing thoughts and really fidgetty at night and can't sleep from 'em. Do you take it in the morning or evening?
You could try some herbal remedies for falling asleep. Valerian, chamomile, passion flower, well those pop into my head, they have teas with them included like sleepytime teas. I'm having the same problem with a similar thing and i've ordered L-gaba because it's supposed to help people sleep by naturally increasing their relaxing neurotransmitter. Not sure if you can combine that with your zoloft though.
do you find zoloft is working for you otherwise?