started out good.....but fizzled

Ran 16 today. Ran the 1st 10 straight through and felt awesome. Had a 10:58 average pace going up until then. I didn't want to stop because I feeling so good but I had to refill my water bottle...the parking lot where the drinking fountain is was completely blocked off with a temporary fence because they had some boat race thing going on. So I had to walk all the way around to find an opening to get to the bathrooms where the drinking fountain is. I decided to skip the bathroom at that point because I really didn't have to go and my pace was already suffering because of the search...so I started back up again and withing 1.5 miles my stomach started rumbling....not good....so I stopped to use the restroom and ended up in there for about 10 minutes....now my pace is REALLY suffering!....I'm investing in a super stock supply of Imodium today!....then I get out of there and the last 4 miles were a struggle because of the horrible stitches that I had in my sides...they would NOT go away. I kept trying to walk and bend over pushing on the stitch...I tried to deep breath (all the remedies I've heard over the last several months)....nothing worked...so I'd walk until the pain was bearable again and then run until it became unbearable again....I did that for the last 4 miles. Ended up walking a lot of it. In the end my average pace ended up being 12:04. I was very disappointed...the 1st 10 went so well....I was on a role! Damn it! The good news is...I can run 10 miles straight now...the bad news is I doubt I'll hit my original goal of finishing in under 5 hours. I keep peetering out in the end. But that's OK...as long as I'm not the last 1 over the finish line I'm good!