What Causes Weakness, Shaky Eyes And Nervous Feeling?

I am a 28 year old female I am 5/5 135 i have a medical history of kidney stones anxiety Low blood pressure not all the time though an d 3 months ago had my second child about a month before I gave birth I had an upper respiratory infection that took along time to get rid of but have been feeling very weak and shaky my eyes feel real heavy and weird I also get real spacey it comes and goes but seems like it's worse in the mornIng I am always really nervous feeling with it as well I find myself not wanting to go anywhere until I have to leave for work in the afternoon and afraid to b alone because I think I may pass out. I have been to the hospital had blood tests done and they can't find anything. Any ideas please help