Hello and thank you for consulting JA,
These thoughts represent obsessional thinking with a compulsive behavior (OCD). This is an anxiety
disorder and his sensitive nature (with mild anxiety, I assume) may be connected to all of this. If untreated it could expand to other similar things like counting tiles on the ceiling, etc. etc.
The treatment starts with several sessions with a cognitive behavioral therapist:http://nacbt.org/searchfortherapists.aspxhttp://therapists.psychologytoday.com/rms/
This type of therapist will help him see why his thoughts are irrational and help him to change them. The therapist will also teach him coping strategies such as relaxation and guided imagery.
You can also work on this problem at home using bibliotherapy (reading books!!). Here is a good book for this: http://www.apa.org/pubs/magination/441A805.aspx
There are also child relaxation and guided imagery books, CD's and Youtube videos.
Finally, if the behavior begins to interfere with functioning (i.e., takes too long to get ready and chronically late, is very upset by his thoughts and behaviors), the doctor should be consulted. There is medication for this for use in extreme situations (but you have not described an extreme situation).
I hope that I answered your question. He will get better and this is easy to treat.