I've done nothing but worry ever since I passed out a month ago, help!

About a month ago, I passed dead out. I had had only 3 hours of sleep and was very dehydrated. I went straight to the ER. They did every kinda test they could think of, and everything was perfect. But ever since then I've been worried sick that's it's gonna happen again. I have very bad Health anxiety and depression. Someone please tell me what I do, it's like I even feel weird, everything also looks weird. Is it all in my head or what?

Hi Help, there was a reason you passed out, lack of sleep and you were dehydrated so as long as you at least keep hydrated you won't pass out.

Neil 

I know but it's hard to believe that when I always feel like I'm gonna pass out..