Hi Alisia,
I know exactly how you are feeling as I have had similar problems where my memory and concentration got very poor and I suffered from daily headaches for a very long time. Thankfully I haven't had seizures.
As the others have said, your symptoms certainly need checking out and I would also wonder about APS. It seems surprising with your history that you wouldn't have been checked for it.
APS is anti-phospholipid syndrome and it is basically a blood clotting disorder where your blood is too thick or "sticky". It can cause all sorts of symptoms including cognitive problems, seizures and headaches. Around 30% of people who have lupus also have APS though it can also exist on its own. Once diagnosed it is usually relatively easy to treat and control by using blood thinners (sometimes just one baby aspirin a day).
In any case I would certainly call your neuro if you have one and, if you don't, I would insist heavily for a referral to one.
Katharine