I ran my 12 miles yesterday. This is my longest distance ever.

It was a good run, but I wasn't happy with my time of 2:20. I really don't think that 5K on Saturday should have affected my long run, but I don't know.
My first 2 miles were 10 minute miles, I am guessing too fast for me. It was interesting to see that every mile, I got a little bit slower. I did feel fatigued about 1/2 way into it.
I am guessing my time would have been better had I run/walk some of it, or more importantly, had I started out a little bit slower. I have this thing though, that I think I have to run the whole thing. My first hm is 2 weeks from this Saturday, and I want to run the whole thing. That's my goal.
OK, I didn't post last night after my run because I got sick about an hour afterwards. I was very nauseated, had diarrhea, and shivered a lot. I am trying to believe it wasn't from my run, but I am just not sure. I felt I was well hydrated. I know I sweat alot, but as it got cooler out, I didn't feel very sweaty. However, I had white salty powder all over my face, forehead, and shoulders. I did drink about 12 ounces of powerade over the 12 miles, and I eat a peanut butter sandwich about 20 minutes after my run. I think that's what made me sick. I am hoping it was a coincidence.
I feel great today.
Any thoughts?