How in the heck did I loose 1" in height?

Ok, I am really starting to be bothered by the fact that over the last 3 years or so I have apparently lost 1". I used to be 5'6 1/2" ,but the last time I went to the Dr. (about 1 month ago for severe allergies)which isn't often my height was 1" less, so I'm now 5'5 1/2" standing up straight. I am very confused by this since I don't know if this is a health issue, "woo-woo" issue or both. My posture is not great, but not awful, and generally I do not slouch much and my abs are pretty strong, but nonetheless I feel like I really need to start addressing this maybe "posture situation". When I meditate I sit up straight so that the energy can flow through me it's just when I'm done I do unconsciously slouch again. Help. Any ideas?.....:)

Love and Light,
Carolyn