5 days after the stomach flu i am still having bouts of nausea and extreme weakness. i just want to sleep all the time. could it be something else?

See a doctor: With something that's 'drawn out' like what you describe, it's time to get professional evaluation. You may have become significantly dehydrated by that stomach flu- and you could be suffering consequences from that. I recommend you go to an Urgent Care center or ER for lab work ASAP. You should have recovered by now from a simple virus, so this needs further investigation and TREATMENT.