An odd one

I had a really odd run today. The weather was beautiful as I set out for 15 miles, ipod on and ocean by my side, no mom guilt knowing that Petru was going to have fun with grandma at Dover Children's Museum. Ah, the life. I really wanted to keep the pace down today. I ran 10 miles @ 7:09 on Thursday (yes, silly me, I am blaming the Nike free's) and although I felt superhuman on that run, I know I am not. My plan called for 15 @ 7:53, and that was what I needed to run. My route around here in New Castle/Rye is filled with rolling hills for at least 1/2 of it, so that was certain to slow my pace down. I started out slow, first mile 7:50, as planned, but then I got into the scenery and podcast I was listening to, and did not realize that I started going faster. My issue is that once I hit a certain pace, I can't make myself go slower. It's silly and it does not make sense, and I really need to work on this. Anyhow, about 7 miles into the run, my L groin started to feel tight. I stopped and stretched it, but the tightness persisted. By mile 10, it moved between the knee and groin, on the inner side (sorry, I have no anatomy knowledge). I stopped again, hopped on the leg (my stress fracture test) with no pain, tried to find a hot spot but could not. I kept on running. By mile 12 all the tightness was gone. No pain, nada, just tired legs (they were tired even at the beginning of the run). So I am not sure what I should make off this. I think I may try a sports massage (never had one, can you believe it?) and definitely foam rolling. I think my muscles are tired from everything I had them do this past few weeks, and I need to pamper them a little. My 1/2 marathon is in 2 weeks, and I want to be able to run hard then. For that, I need to slow down now. Ah, so hard. This is the time in training when I am running strong and I want to push it even more. This is also the time when injuries start to appear and I need to be careful. Will I be able to? Will see....