lightheadedness after gastroenteritis: dehydration?

Hello all,

I'm a normally healthy, 25 year old school teacher who had gastroenteritis about 4 days ago, which I assume I caught from one of the kids I teach.  I'd say I had it pretty easy, considering: only one day of vomiting/diarrhea.  In the days before the attack, however, I was suffering (and continue to suffer from) a pretty bad cold.  My stomach feels fine now and I'm able to eat the normal BRAT diet, but my main complaint is a persistent lightheadedness and lack of energy which prevents me from doing much of anything useful.
Could this be dehydration?  During and in the days after the attack I drank liquids, but probably not as much as I should have (I read somewhere that I should have been drinking 16 cups, I know I wasn't having THAT much).  I've also been taking tablets to replace my intestinal bacteria.  I feel really lifeless and useless and just want to get back to my own self, and quickly.  Can I stay in bed today and drink lots of energy drinks/water to combat this?  Or should I see a doctor/go to an ER for an IV? (keep in mind I live in Spain, and if there's anything I can do at home to treat myself that would be preferable)
Thanks so much for anyone who can advise on this.

Emma

[boron]

Dehydration is possible. Beside lightheadedness and weakness, you might noticed a less amount of dark-colored morning urine with a stronger smell than usual, dry mouth, dry skin and prolonged skin turgor (skin fold on the back of the hand flattens slowly, after you pinch and release it.
http://www.allhealthsite.com/26/complications-of-diarrhea-dehydration-malnutrition-etc-2/

Not energy drinks (no coffeine, taurine!), but sport drinks, like Gatorade (with salt and sugar, which both enhance water absorption) can quickly rehydrate you. Use common sence about how much to drink. When you feel that you excrete all water you have just drunk, well, then you know, you had drunk enough. Your morning urine should be at least 200 ml, and bright (translucent or yellow, not brown). You might also buy an "oral rehydration solution", it's available in any bigger store without prescription. Names are Pedialyte, Rehydralyte or so... they are ment for rehydration after diarrhea.