As weak as a day-old baby

i haven't been ill for a long time and this is just freaking me out!

it started on monday, what i thought to be a minor case of  runny nose. but it got progressively worse on tuesday and i had to go see a doctor on wednesday.

by friday, my nose wasn't runny anymore but i was feverish and had a terribly sore throat. went to the doctor again.

now, sunday, the fever and sore throat had subsided. by right i should be feeling much better but i'm feeling so damn weak.  i dun understand it. it's never happened before. and it's not as if i've not been eating. if anything, i've been eating more than usual and expanding less energy by resting all day for the past 5 days.

am i getting SO old that it's taking such a helluva long time to recover????