B.L.
First, (( hugs )) to you...this is difficult to go through. My husband has seizures also.
The fact they've done all those tests and they are coming back negative may actually be a good sign - that means there's nothing scary like a tumor causing them. My hubby was at least 17 or so before he started having them out of the blue, no reason for them that doctors have found.
Finding the right medication to control them can take some time because different things work for different people. He's on his third combo and has finally found one that seems to not only stop the grand-mal seizures (convlusions) but also the petit-mal (those ones are hard to explain without going to great length).
For great information on the different types of seizures and the different treatments, check out www.epilepsyfoundation.org.
Finding a real cause is rare, but there are some things I have learned that are VERY important: take those meds on time, eat regularly, and most definitely get enough sleep every night. My husband is very well controlled on his seizures, but if he gets almost no sleep then misses a dose, he'll have clusters of petit mal seizures for a day or two that wear him out.
Feel free to message me, and good luck with this.
P.S. - I also have three girls, aged 9, 6 and 3! :-)