The best thing I've done that's put my mind at rest is to ask to be alone in the bedroom when changing, whilst leaving the bedroom door ajar. Whilst getting changed I also do a quick search of any places where I think cameras may be; any doors that may be ajar, clothes casually thrown over chairs etc., that might conceal a camera or phone. I don't touch anything, I just use my eyes.....and my butt. Seriously. If I'm suspicious of anything that might be thrown casually over the chair, I sit down on the chair. That way I can 'feel' if anything's concealed there.
It sounds funny but it puts my mind at ease.