Eeg disgnosis indicates that i'm normal but i'm diagnosed to have epilepsy because of the seizure. can you explain?

Go back & ask again: Every normal eeg carries the disclaimer "the absence of epileptiform discharges on a routine eeg does not rule out the presence of a seizure disorder." about 1/2 of epileptics have normal interictal (between-seizures) eegs. No competent neurologist would call you "normal" based on an eeg. You may well have misunderstood. Request clarification. You're the patient, not the eeg.

Limited value: Eeg is like listening to an idling car engine. It may sound fine but start backfiring in a stress setting. Oftentimes eegs are normal except during the seizure. We are lucky sometimes to induce seizure discharges on eeg by activation, but up to 20% of eegs remain normal even in patients with definite epilepsy. If repeated eegs show worsening, that may indicate a progressive disorder.