Anita,
I am no expert on this issue and will talk with Walt (my DH- FP Doc) when he gets home for his input but at age 3 weeks I think it is pretty normal for this to happen unless you are talking about the whole top of the ear folding over, covering the opening of the ear. As your baby gets older the ear cartilage will become stronger and larger and will more than likely "stand up" on its own. I have seen this in newborns frequently.
If it is the more severe of the two, covering the ear opening and especially if you had this issue, then you may be dealing with something more involved. I just googled "baby ears folding" and saw this web-site. I do not endorse the treatment or the site, by any means, but it may have some info. I would recommend you talk with your Pediatrician and see what they recommend; watchful waiting at this age is not unreasonable. It may require surgery in the future if it does not correct on its own.
http://www.earbuddies.co.uk/pws/Cont...orward=content
Keep me posted,
Dana