From the history that you described, it sounds as though you suffered a great deal of traumatic injury to your brain three years ago. As you suggested, there is a high likelihood of developing seizures after traumatic brain injury. From the history you have provided, there are some questions that would be helpful to know.
For instance, are you currently taking anti seizure medications? Have you had any episodes where you have passed out? Do you even wake up and notice that you have lost control of your bowel or bladder function? These questions are important to gauge whether you may have had seizures that you didn't realize. If you do not feel that you have had any seizures since the injury, and the doctor
did not prescribe you anything for seizures (such as dilantin, keppra, or other seizure medications), then the likelihood is low that you will develop seizures three years later.
Of course, without a full medical history and clinical exam it is difficult to say for certain. For this reason, it is important that you be evaluated by your primary care doctor
who will be able to better evaluate your medical history, and current symptoms and decide upon the appropriate work up if necessary, which may include lab tests or imaging.