swimming pain

I have been swimming at the lake in Grantsville because it is close to home. with my hectic work schedule I can get evening swims in before it gets to late. Sundays swim was a nice easy swim there was only one boat on the lake and just a hadfull of people fishing from the shore. I hopped in and took a temp reading it was 68.9 degrees and I was off. I swam counter clockwise around the lake so I could keep my eyes on the shore to get more yardage out of a lap. With fewer people fishing from the shore I could stay closer. As I was swimming Colton was paddling for me and he kept hitting me with the kayack and with the paddle. I never stopped to see why but when I finished one lap I stopped to get a drink and he said "Dad did you not feel me hitting you?" he wanted to see if I wanted a drink and that was the only way he could think of to get me to stop. Run your poor dad over with the kayack and hit him with the paddle! I grabbed a quick drink and started for another lap. I got half way down the front of the lake and noticed that my lower back was bothering me really bad. I turned towards the middle of the lake and then headded back towards the beach where my family was waithing for me. the only thing I can think of why my back was bothering me so bad was because I was sighting 10 times more than I usually do to keep myself colser to shore. I also brings me to the Deer Creek 10 mile event this weekend. I may change to the 10K distance because I have not been swimming as much as I need to. the last thing I want is to be pulled because I cant finish. We will see what this week brings for me in the water and I can make an educated discision for the race.