Like I said, I am not sure what went wrong. I ate a good breakfast a couple hours before running and drank lots and lots of water all morning leading up to my run since I knew it was hot and the sun was really hot. I drank a small glass of gatorade before walking out the door to run as well. I carried a small gatorade and a water bottle with me.
I had a good bit of hills in my first 4 miles, but most of which I do when I run my long run. I didn't drink anything till I was about 4 miles in but was drenched in sweat. I usually don't carry a drink in the morning when running up to 5 miles so I really didn't think I needed it. Once I started feeling bad I started to drink a bit of water and then drank the whole gatorade (small sport size) but I think it must have been too little too late.
I walked a good bit in the next three miles, but tried to get in a little bit of running as well. I did decide I would run the last mile home if I could and was able to and it didn't feel too bad. I was absolutely exhausted when I finished though.
The only thing I can think is that because of the heat and the hot sun I should have continued to hydrate early on in the run, instead I waited too long and I couldn't recover fast enough.