Yes, the media and fashion industry idolize a particular thin look for high-fashion clothes worn on runways. Yes, this is BS and stigmatizes those who fall in the statistically normal range. Yes, perfectly healthy girls and women develop complexes about their weight as a result of this, and it is terrible.
But, as 20:41 said, it's also true that regular clothes are not designed for thinner women, and our needs count too. I'm sorry that bigger women get such a raw deal, but the real issue here is society's treatment of women -- all of us. In general, if we were not objectified and judged primarily as sex objects, and if we didn't tend to internalize that objectification, our clothing and other needs would be more likely to be met and we would not be reduced to this silly infighting. Curvier ladies, the answer isn't to demonize thinner women or to assume that every thin person has an eating disorder. I can't change my metabolism any more easier than you can change yours, but we can work together to change the way society views us and the way we view and treat each other.
OP, I've had pretty good luck at Club Monaco, which stocks size 00 (and their size 00 is smaller than, say, Ann Taylor's, which does run big). I'm 5'7" and 116 lbs, though, so it is easier for me. I used to be thinner, around 107 lbs, and clothes shopping was impossible in the States -- but not in Asia, where smaller sizes are normal. With your height, you might have to shop around, but if you locate some Asian brands that cater for tall women you may have it made. I have had good luck with the Taiwan-based brand Shyangan.
Good luck. I feel for you.