Popular portrayals often show people of the middle ages as dirty and unconcerned with hygiene. But how true was this? Would a wealthy European noble in say, the high middle ages, have worn the same cloths several days in a row before it was noticeably dirty and sent to wash? Or would they have had a more modern sensibility of wearing an outfit only once, or mayyybe twice before it was washed again? Was it a faux pas for a noble to be seen wearing the same cloths twice in a row, or to two different events in a short period of time?
The problem with the modern idea of washing clothing is that all our clothing touches our bodies directly - there is hardly anything between you are your shirt, normally. However, how often have you washed your winter coat? You probably don't wash it often because it's layered over another piece of clothing - your shirt and/or sweater.
Think of most medieval clothing more like a winter coat than a shirt or dress. Beneath the dress or doublet or whatever else was worn was the shirt/chemise layer. The shift/chemise/shirt was always worn beneath the Tunic/Doublet/Dress/ect. It's an undershirt but also worked to act as a protective layer between the skin and the wool/silk/ect. It is almost always made of linen with little exception.
Now, with that being said, the over layer would be washed far less frequently than the shift layer. The Goodman of Paris mentions "clean shirts" to be kept out for her Husband but it makes no mention of how often these were cleaned. In Daily Life in Medieval Europe it mentions that clothing in the Monastery was picked up on a Tuesday to be washed and returned on a Saturday. This reconciles with what I recall of a weekly washing in most Medieval English homes. However, this would be the undergarments - of which you might have two if you are poor (one for wearing while washing the other) or more if you are rich. However, the undergarments were washed pretty regularly while the overgarments might not be.
This does not mean the garments smelled - just like your winter coat probably doesn't smell. Just that they didn't need the wash as badly as the shift would.