You have nothing to be ashamed of. It is good that you have learned ways to improve your posture.

It is possible for you to have a discussion with the people you share your apartment and explain to the fully what condition you have and how it distorts your spine you need them to understand that you feel embarrassed?

Windows can always be covered by lace or some type of light curtain that still lets the sun in but blocks prying eyes. The tensions that you experience at home is not good for your back and anxiety.

People who stare are rude. Maybe if you asked them if they would like to talk to you about something it would break the ice. Otherwise tell them to take a picture because it lasts longer.......