passing out...

I am in the midst of frustration, being totally scared, and confusion all at the same time. Lets start from the beginning in fast mode. From as long as I can remember I have been getting lightheaded whenever I stand up. I ask people and they say "Yea it happens to me too." So of course I think nothing of it. I just stand up, lean over and let it pass then Im good as new. Inside I really didn't think it was normal for this to be happening 5+ times a day. People kept assuring me it was normal.
This lightheadedness comes and goes so sometimes I can go a couple weeks with no problems then it hits me for months at a time where its 10+ times a day. Again I just lean over, let it pass and on with it. Well Tuesday was a different story.
I had eaten breakfast and was waiting for Kendyl to finish so I sat on the couch and watched price is right. She was finished about 5 minutes later and I went to get her. I stood up with no feeling, walked over there with no feeling, picked her up and BAM! I frantically without being able to see tried to feel for a wall to brace myself. Next thing I knew I was waking up on the ground with her on top of me. It was a pretty hard fall, as in 2 days later I still have a kinked neck and my head still hurts. I went to the doctor where I got xrays, EKG, urine, blood and blood pressure testing all done. Here are my results: Drink more water and add salt to your diet!
I have to say I was more frustrated after hearing this than not knowing what was going on. Reason being, I drink tons of water and all my food is pretty salty. So faithfully I made a point to drink extra water and actually add salt to each meal.
Well this morning I woke up, ate my breakfast, again waited for Kendyl to finish her breakfast. Got up to get her, and before I even got to the kitchen (seriously 8 steps away) I got lightheaded but found a wall. Next I knew I was waking up on the floor. Must have hit pretty hard again because I knew rug burn on my knee and my headache is back.
I am seriously so frustrated because passing out is the next level. I could deal with the being lightheaded. Passing out I can't. I am home alone til at least 2 everyday. I have a baby here I am supposed to be taking care of. When I fell with her in my arms it scared me. I cried for probably an hour. I am so thankful she stayed on top and wasn't hurt a bit. I am scared because honestly, I have no idea how long im "out" for.
Here is my plea....if anybody knows anyone with any similar symptoms PLEASE let me know. I am determined to figure this out asap. Thank you! PS, no im not pregnant since that seems to be the first question EVERYBODY asks!