Two months back I had a seizure that was the first...

should you continue taking medication ?
yes you should , seizures paitnet even if not diagnosed yet should take medication for long term before trying stopping it , because seizures cant happen in normally functioned human body , so if you tests came out normal now , then doesnt mean your diagnosis is finished , so our recommandtion is the following :
1. continue taking the medication 
2. keep on visit the doctor and do regular tests 
3. usually doctor will give you medications for 18 - 24 months before stopping it , and it can be represcriped if seizures happen again 
causes of seizures :
1. changes in brain electric function
2. low blood sugar 
3. medications overdose or side effects 
4. brain injuries and infections 
5. brain tumors
6. Epilepsy