Seizures or faints?

I have a question about the relationship between fainting episodes and seizures. Yesterday I blacked out and experienced seizure-like symptoms according to my sister (the only person who saw what happened.) Violent shaking, strange choking/groaning noises, crossed eyes etc etc. Prior to this I'd experienced intense nausea/lightheadedness and a panicky sensation. When I came to, I was drenched in sweat and completely disorientated, exhausted, my muscles were cramped and I had a horrible headache. I was taken to A&E and had a few tests done, the usual basic stuff like blood sugar/pressure. My BP was absolutely fine but my blood sugar apparently was ever so slightly low (it happened just after I'd got up and while I was making breakfast.) This has happened to me once before, 2 years ago at a concert. Again everyone who saw me faint described me having had a fit while I was unconscious. I was told it was probably just the product of tiredness/stress and not to worry too much, I'd just started university so I'd been drinking a lot, not sleeping well and so on. However this time it's happened while I'm otherwise pretty healthy- not sleeping badly, eating okay, and I'd not been drinking recently or anything. Again though the doctors I saw didn't advise me to see a specialist as they said fitting during a faint is relatively common; to be honest I'd never heard of this until I first experienced a blackout, and I certainly don't know anyone else who's ever experienced the same thing. This also incidentally happened while I was using an ab toner belt, I was a little concerned at first that that might've actually caused it, although it seemed a bit far-fetched. I am a little worried though- first time around I could dismiss it as a one off, but now I'm concerned there might be an unerlying problem that needs investigation. Is this normal or should I go and see a neurologist? I'm a 22 year old female btw if that's of any relevance. Thanks for any help...