i think that is low mileage for it to be the CAT. but the dealership or mechanic can determine that easily.
could it be the brand of gasoline? some poor quality gas may contain more sulfur although i have only "heard" this as a reason for the smell and haven't seen this myself (never had the problem, but i only use shell or chevron if given a choice)
if your car was running really rich, that would increase the likelihood of these smells, but you would normally get a CEL if that was the case.
if you can't attribute this to bad gas (or you don't think it could be the reason), you might have to take it in to find out if it's really bad.