Help me I'm at the end of my tether

I am a 33 year old father of three beautiful boys but my world was turned upside down in 2010. My eldest son was five when he became seriously ill. After his illness he was left with a neuromuscular disorder known as dystonia. He spent 10 months at the children's trust in Surrey where he had to learn to walk talk and eat again. He hospital never had a diagnosis for him. While we was staying at the childrens trust my second son fell ill with simular symptoms. He had crossed eyes and was very lethargic. It knocked him off his feet and he was very wobbly on his feet. He was then discharged from hospital with no diagnosis..... Again. Then very recently my youngest son who is 21 months old fell ill with the exact same problem. Crossed eyes very lethargic. He is out of hospital now. Once again with no diagnosis of the problem. CT and bloods where cleare except that he had a nasty virus and had a temp of 39.2.. But now all I do is worry. Worry worry worry. He has been himself but now I can't shut off and enjoy my life. Its hard enough not knowing what the cause is. Belive me my eldest was a lot worse than the other two and had dozens of tests. But all where clear. I can't stand it anymore. I just want to live a normal life. Has anyone had this problem in their family before. Please help me. Ps they tested my eldest for any genetic problems and all was normal. Its killing me I just want to see if anyone can help us. Thank you.