If you're facing some sort of compulsive behavior, don't just engage in it. Realize you're engaging in a battle with yourself, and these wars aren't winnable. Try to break it down and find what it is that you're REALLY looking for. There's a reason for it, and more than likely it's a good reason that's just being fulfilled in an unhealthy way.
For instance, fetishes are generally not about the items themselves but what they have come to mean to the person. A pair of underwear is nothing exceptional all by itself, so the question is, "what does it REPRESENT to you?"
Did someone you admire in some way wear a certain brand or size? Are you connecting attributes of that person (maybe someone who was popular, good-looking, the kind of guy you "wanted to be" and so on) to them? If so, it's likely that once you make the connection and see that it's a misdirected sexual or self-esteem issue, the compulsion may well go away all by itself.
Instead of attaching sexual feelings to the object of the fetish, like a pair of underwear, you'll be able to say, "Aha-- that's not what I'm looking for at all!" and let it go.
So, (1) admit you're looking for something that the compulsion seems to offer, (2) really break it down to see just WHAT it is that you're seeking, and (3) see if there is another, more healthy way to find what it is you are truly looking for. Survivors live in a very fluid, confusing world, and what looks like an apple is often an orange. Hope this helps.