When Not To Tell Her You Wear Lingerie
On the whole, I advise men who wear women's lingerie to always tell their partners, but sometimes that's just not entirely practical or suitable. There are a few situations in which I would not advise telling a female partner that you wear women's lingerie.
If You're Not Considering A Long Term Relationship
In an ideal world, all lovers would be candidates for a long term relationship. However in the real world, people sometimes get together with the full knowledge that this will not be an arrangement they will be continuing long into the future. In this type of arrangement, I don't think it is necessary to share the fact that you wear lingerie unless you really want to and unless you trust this woman.
Of course, in some casual arrangements it may actually be easier to share your love of lingerie because the stakes are not as high. At any rate, I don't think this is a 'Must Tell' scenario.
If She Has A History Of Being Vicious And You Don't Trust Her
Now really, if you're with the kind of woman you can't trust with intimate knowledge then I suggest that you make your way toward the exit with all due haste and don't give her any ammunition on the way out. Some people just love to make enemies. You'll never have a happy and fulfilling relationship with this kind of person because eventually she'll turn on you and make you the enemy and then all bets are off.
If You're Not Yet An Adult
Yes, teenagers sometimes wear lingerie too. If you're a young man who has yet to reach your mature adult years, but wear lingerie, don't feel pressured to tell your girlfriends you wear lingerie. Why? Because relationships at this stage of life are generally much less stable, due to the lower maturity factor of both parties and young women may not have the experience and presence of mind to handle the news with sensitivity.
Of course, all of the conditions I write about here are subjective. When one considers oneself an adult is a rapidly changing benchmark in modern society, where people often refer to 21 year olds as 'kids.' Use your own best judgment.
If, on the other hand, you want to wear womens clothing and tell people about it, then go ahead. You need not be ashamed of doing so.
These are examples of the few situations where I concede that a woman doesn't need to know. Long story short, if it's not a 'serious' relationship, then I don't think you have the same sort of obligation, or indeed, any obligation to tell your partner about your love of lingerie.