Dizzy!

I did a 10 K today (Well 6.5 miles so a bit more). I ate before I left, and drank 2 l of water and had some coffee. I did my run and knew I had to get some things from the grocery store so I brought a mini can of tuna and ate that on my way out of the gym. (I am sure people at the grocery store thought there was a stray cat loose somewhere....No shower after 10 k and a can of tuna....nice).
When I got home I started to make my lunch for the next couple work days, while at the same time making lunch. (I had another L of water during and after my run as well). I was eating about 20 minutes later (some of the homemade cauliflower soup, broccoli with homemade salsa and 1/2 cup egg beaters on the side)When I was 1/2 through eating and got up to get the mustard (I have a ridiculous addiction to the point it grosses other people out since I put it on very odd things) to put on my eggs. I got sooooo dizzy. And not for a second...for almost a minute...I thought I was going to faint. Now I have fainted before (out cold and flat on my face) but I was super sick with the flu at the time. It passed but now my head feels funny. I am not sure what the heck. I have eaten lots, had tons of water-hmmm-
2 questions
1)What do you think this could be.....
Oh and someone told me recently I drink too much water? WTF
So I looked into it and it is hard to find a straight answer.....I drink on average 6-7 L a day....-I also chug my water usually in about 1 L increments (6 or 7 times a day). I am so busy, especially at work that I don't have time to sip anything (I eat most meals at work standing up that's how busy it can be).
2) is this too much? (Is it too hard on my kidneys, especially when I chug such a large amount at a time?)
I am off to straighten my hair and go out to dinner with a friend who is in town on training for work......I hope it STOPS raining...it is getting sickening.