There have been 2 cases of severe seizures within the last 2 months, both times the hospital blamed it on low sodium but couldn't find anything else wrong. i have been eating a lot of salt already, could there be something they missed?

You should request evaluation by a specialist like an endocrinologist if the low sodium is so low as to cause seizures and you do not have issues with drinking water more than normal. There is underlying imbalance in the salt exchange in your kidneys that is usually modulated by hormones that probably should be evaluated by blood tests.

Your sodium level would need to be very low to cause isolated seizure activity and if this is well established, an underlying cause must be sought. You likely need to be protected by anti epilepsy meds. Get an appointment with a neurologist. Avoid driving, activity at heights, power equipment