What Causes Grand Mal Seizure?

During a session at the tattoo parlor i had a grand mal seizure where my eyes rolled into the back of my head and my leg muscles contracted and released twice. The whole episode lasted 20-30 secs. Immediately before I lost awareness my stomach felt empty and i felt light headed. I've had that feeling twice before over the last year and a half when I working out in the morning but did not have a loss of awareness or muscle control those times. I've had a headache for 3 days since and have had headaches 3-4 times a week for several weeks before it happened. The headaches are not severe, just a dull pain. Two uncles and my grand father had epilepsy but it was brought on by head trauma. Is it possible that it was a diabetic seizure since every time I have felt like that it during something that put stress on my body and I had little or nothing to eat? Or is it likely that it was epilepsy or something else? Should I hurry and get a appointment with my doctor?