Mellay,
I think it's not unusual when you're still this close to the time of your treatment to be extremely sensitive (maybe to the point of obsession) about possible warning signs. However, with the passage of time (and hopefully some all-clear checkups along the way), I think you will start to see this feeling subside a bit and give way to just a common-sense level of vigilance.
I remember being with my whole extended family during the first Christmas season after my treatment, and looking around wondering if it would be my last Christmas like that. However, as the years have gone by with many more family gatherings, I've realized that cancer was a reminder of my mortality, but it may not ultimately be what "gets me" -- it could be a heart attack, a car accident or something else entirely.
I also understand your feelings about wanting to see your 8-year-old graduate. Right after I finished my surgery, while I was waiting to start radiation, one of my nephews was born and his parents named me as his godmother. I took that as a sign of their faith that I would be around for some time to come. Just a couple of weeks ago, I received an e-mail from his parents asking if he can stay with us for a few days while he visits some colleges in our area that he may want to apply to (yes -- that much time has passed).
Wishing you many years of health,
Cathy