Thanks for your question about how you are feeling. I am not a doctor and cannot comment on your seizures, but it sounds to me like you have burn-out. From what you describe, you have been a rock for many people in your family and the appreciation from family members has not always been what it could have been. Your resources are running low because you give all that you can to those around you who you love - when you tell them how you feel, and your body reacts to the stress by having a seizure, even then they tell you that you should be more appreciative of what they do, and this is asking for you to use up more of your resources. Using your resources for those who you love is fine, if those who you love return that love and refuel your own resources so that you can continue to fight for what you believe in. It sounds as if you are out of resources, with no means of replenishing them.
I would suggest that you source yourself a local hypnotherapist, who will help you to learn how to truly relax very deeply and to seek that inner strength that you had some 12 years ago. It is still there and it belongs to you, because no-one can take it away from you - but it has been buried underneath the exhausting concerns for others. It is time to take time for yourself and allow yourself to enjoy what you enjoy, even if it's only for 20 minutes every other day. Some people consider this to be 'selfish' - but without being somewhat selfish, as you have found, the 'self' simply cannot remain strong. Find a therapist who will make a CD for you, so that you can listen to it at home. Then you can use the powers of self-hypnosis to be as strong as you wish to be.
Hypnosis is a deep sense of relaxation, where you are always in control. You will not be 'made' to do or say anything that you do not wish to do or say; you will hear all of what your therapist says to you (unless you fall asleep, in which case your subconscious mind will continue to listen) and most people find it extremely relaxing and enjoyable.
The 'negative' side of this is that you may become much stronger in yourself and therefore less accepting of the way in which people around you treat you - people who expect you to be taking care of them may not be very enchanted by the fact that you are taking a little time for yourself - the change in dynamics of relationships can therefore be a consequence of this therapy, which you should really be aware of before you begin.
I wish you all the best - take care of yourself for a while, you deserve it. Sarah