Also, I don't know if you had insomnia before taking Zoloft. Your insomnia now could be caused by you sleeping so much during the day. We'll say your sleep clock could be messed up from sleeping so much during the day. Once you get back on track, it could get better.
I am not an expert but I can give you a few suggestions. As always ck with your dr. I would try the med at night. Give it a chance. You won't know if it makes your insomnia worse until you try. You should not need to sleep your day away and this will definetly interfere with school. If taking it at night doesn't help with your daytime tiredness and pm insomnia, it is likely that you are on too high of a dose. Some people are more sensitive than others when it comes to meds. A little may work for you whereas someone else may need a much higher dose to work. Keep in mind that not all meds work for all people. Meaning, if Zoloft isn't the med for you, try a diff one, working with your dr on this.
I hope you are seeing a psychiatrist and not a general practitioner. A psyc dr is much more knowledge in cases like this. They will work for you to find the best med. It does sound like the Zoloft is too high in dosage but try it at night to see what happens. I'm sure you want to take care of this before school starts. Make an appt with the doc please. We are here if you need us.