Jessica,
How long you WANT to remain stealth? While your breasts WILL eventually become obvious to everyone, that doesn't mean you must break stealth. Gynecomastia is more evident today than ever and develops for no apparent reason on men of all ages, but especially those over 40. If you continue to present yourself as a man in the way you act, dress, accessorize, carry yourself, male voice, and converse on masculine subjects, you might possibly be able to remain in stealth indefinitely. Obviously having breasts will invoke questions in people's minds, but if anyone asks, just tell them your doctor prescribed some medicines that had a side effect of gynecomastia, which is the truth. If they don't know what gynecomastia is tell them to Google it. You don't have to explain nor reveal that you're in transition.
IMO, you sacrifice the ability to remain stealth when you shape your brows and grow your fingernails. These are things you can't take or wash off if someone comes to the door. Other actions when done in public such as wearing makeup and earrings, applying feminine movement, speaking in a higher tone of voice, changing your name to a female name, etc., are all confusing for people, and they may not know how to interpret your actions, but they know you've violated a gender line. The evidence of long term HRT in having breasts and a female physique only proliferates their suspicions. That doesn't mean you'll pass as a woman, only that you've gone beyond the social norm, if that makes sense.
The one person you can't hide from is your wife, whom I'd assume sees and touches you daily without a shirt on. She knows what budding breasts feel like, especially when the nodules start to grow behind the nipples. If you're at that point, I doubt your wife hasn't noticed. She probably just doesn't know how to confront you with the question of what is going on. She may or may not suspect you're transsexual.
