the symptoms you described are indeed symptoms of low blood sugar. meaning the evening meal or bedtime snack were not enough to last him through the night and he utilized his glucose stores, and the body is trying to burn some other stored energy.
If he throws up the gatorade i wouldn't give it to him. just because you are playing outside doesn't mean you need gatorade. some people can't tolerate sweet drinks when playing sports. if you are concerned while he is playing and sweating, cut the gatorade in half or quarter with water. and make it a weaker drink. that should take care of the throwing up during exertion. 3/4 water-- 1/4 gatorade etc.
as for his frame, weight, and eating regime...I would say hallaluah!!!!
If you look at the statistics and what doctors recommend about eating, you will find that they all recommmend 6-8 small, light healthy meals during the day. and that is exactly what your son is doing, naturally. And it seems to work for him, mostly. The only problem is that you need to make sure to have him eat before bedtime.
when i have brought concerns about my oldest very thin son to his pediatrician, with all the concerns you described, he asks if he is eating? WELL, YES. is he playing? WELL, YES. He has a high metablism, feed him at bedtime, let him play, overall he slowly gains weight. as your doctor i am not worried. so, i stopped worrying. AND FED HIM, or really continue to let him eat at meals and alot of healthy between meals snacks.
the only thing for you to worry about, is the low blood sugar, which the doctor is correct. there is nothing really to do but feed him and watch it. there is not medicine or really anything to use to intervene.
for his bedtime snack, give him something like a peanut butter and jelly sandwich and a glass of milk, yougurt or crackers and cheese. he needs something with protein to last the night. it takes the body longer to digest the protein. the body digests the jelly first(simple sugar), bread second(comples carb) and the peanut butter (protein) later. so he gets an even and constant supply of energy while he sleeps. this should take care of the problem of the morning symptoms. if he does have morning symptoms, try giving him a piece of hard candy to suck on to get some quick sugar in his system, until he can hold down a meal or a swig of juice or milk.
i would also write down his diet and activity for a while in a journal, to see if there is a pattern to the times he is sick in the morning and your interventions. then at the next doctors visit, bring your journal, discuss it and get guidance. you may want to see a dietician, nutritionist, or diabetic educator to see and understand how the body uses food for fuel and to mix your carbs and proteins better, so he doesn't get sick. other than these interventions, there is not really anything you can do for a low blood sugar. if you like and trust your pediatrician, then he should have no problem giving you a referral to the diabetic educator or dietician for your questions to be answered. if however, you feel your doctor is not addressing your needs, or explaining things for you to understand then find a second opinion.
i have noticed, on this forum, that everyone recommends that you always "find another doctor" implying he did nothing. when in fact, there is nothing wrong with the advice the doctor gave you, it just wasn't necessarily what you wanted to hear or it was accompanied with little education and explanation,or he didn't explain his thoughts well. i am not implying that you should stay with you doctor at all costs, simply saying the advice he gave you while it didn't educate you well about what may have been happening, was in fact appropriate. there is indeed nothing to do for low blood sugar but feed your child and educate yourself about what you suspect, and watch him. the doctor can't really tell you anything until he has more information to go on anyway, hence the journal. I stronly recommend the journal before you return to the doctor or get a second opinion. Then you will have armed yourself with some hard data about what symptoms you are seeing and how often backed up by diet, amounts and kinds of fluids and activity at the time. you could even weigh him every week and document that. you can also document how often he urinates (about 5 times a day or 10) and whether his bowels are regular.(have you gone #2 today?) then the doctor will have more information to go on and be able to judge better about whether blood work is needed.
i will give you another example. i presented to the doctor for my yearly exam. my blood pressure was high. now why would my blood pressure be up at 33years old? could be that i am anxious about the coming coochie exam? salty food the night before? etc. now, the doctor can't prescribe something for one blood pressure (well, he could but shouldn't). So, he instructed me to take my blood pressure for a month and record it in a journal, and just observe how i feel etc. take it in the morning, at work, while busy, on lunch break, before bed--etc. and try to cut down on my salt. so he could get a clear picture of my blood pressure across a month while doing various amounts of exertion etc. and then re-evaluate. Well, guess what, consistently, I was high so had to be placed on blood pressure medication at the ripe old age of 33. have been on something for about 4 years now. the point i want to make is that sometimes, waiting and observing and a re-evaluation is appropriate.
i hope all this helps to calm your anxiety. BTW, the really skinny older son, is 13 now and is still in the bottom 25% of the growth chart for weight in his age group. Fine for heighth. My other two sons, while not quit as skinny as him, are still below 50% for weight on the growth chart for my 11 yr old, and 8 year old. They also are on swim team, take gymnastics twice a week, ride their bikes, run around and play. They do indeed burn that energy up, and all three are grazers. All have high metabolisms and all are skinny compared to all the other kids in the neighborhood. we occassionally have problems with low blood sugar, but for the most part, i manage it how i have suggested for you. you really didn't mention other diabetic symptoms, or other problems like unexplained weight gain, or symptoms of thyroid problems. I would suspect that your physician, while not informing you, would have ruled them out from your exam and what you explained to him about your concerns. while you can have blood work done, again I would keep a journal first and then make a follow up appointment to review your concerns, and you will have some documented evidence to discuss. I am also an RN for 15 years, if that makes your feel anymore secure in my advice
Good luck, and trust your instincts,
L.