Re: child has bump on collar bone and has had no injuries?
okay, don't freak out! i completely understand your fears, but your son's symptoms don't have to be the worst case scenario!
the rash could be coincidental.... a lot of 6 year old boys (and girls) still have wiping issues (if they wipe at all) which could lead to getting a rash on his bum. dry skin can lead to skin rashes as well, and the bottom area seems to be the most neglected area for lotioning, so a dry skin rash on the bottom is quite common in children too (my two girls get it all the time until i get smart enough to remember to put lotion on their bottoms after bathtime!).
swollen lymph nodes are also quite common in children, especially during/after a bout with a nasty cold.... and sometimes they stay swollen for quite a while even after the illness is gone.
as far as the cough/cold on and off for 3 weeks.... with all the weather changes that are going on right now, i'm always shocked when i meet a child who ISN'T sick with a cough or cold! my two have spent the last almost two months fighting off coughs and colds! i think they might have had a few days here and there where they didn't have any symptoms! it's just that time of year!
and last, his being tired all the time.... could be if he's coughing or can't breathe through his nose, he's probably not sleeping well at night. a good dose of nyquil, robitussin, any other cough suppressant/decongestant can really do wonders for a child's sleep! if you're anti medicine, a nice cup of hot honey and lemon is great for soothing a cough!
i hope you don't think i'm blowing off your concerns.... i just want to ease your mind a bit. mystery bumps and prolonged illness can be scary to think about, but they don't have to be! i hope everything goes well at the doctor. let us know what happens!