Hi Michelle,
I'm sorry that your son is going through a hard time but I can remember it very well. I was 10 yrs. old (44 now) when I started having absence (petit mal) seizures where I would just stare for a few seconds and then I was exhausted and would sleep most of the day but before the seizures started I had wicked migraine headaches which I found out are connected to epilepsy for many people. Also many people who are ADHD end up having seizures do to their medical problem.
Often when I get a stomach bug, cold or virus of some type I end up having many more seizures because the virus throws my body chemistry off. If your son has the stomach bug have him eat only chicken broth, and drink hot or cold tea. I was sick with it for 3 days. I ask myself if the migraine headaches are what's causing your son to feel nausea and get sick. It happens to many people.
Since epilepsy runs in your family my advice to you is to have your son see an epileptologist (Dr. specializing in epilepsy) I've had the best luck with an epileptologist at an Epilepsy Center which are at many University Hospitals. Also you should have the Dr. do an e.e.g. on your son to find out if he's having seizures. Try cutting him back on sweets, carbs, and starch foods and keep him away from nutra sweet (aspartame) all of these types of foods and beverages can trigger seizures and nutra sweet causes more electrical activity in the brain. I found that out the hard way when I bought diet soda and had many more seizures.
Try putting your son on vitamin B12 it has been great reducing my seizures and you can buy it over the counter. Also take note and keep a calendar writing down what time your son had a seizure along with a description by doing this the Dr. can often see a pattern as to what days of the month or what time of the day or night a person is more likely to have seizures. If the weather is bad outside that can sometimes cause seizures for some people also so take note if there's a low pressure outside.
I wish you and your son the best of luck and May God Bless All of You!

Sue