I'm always amazed they don't (have to) add a flash on the packaging to highlight ingredient changes. A family friend has coeliac disease, and the Coeliac Society send her booklets saying which products are safe, but the tendency of companies to alter ingredients makes her suspicious of relying on the booklets between updates.
Guilt - you have my endless sympathy in dealing with that. I'm not very articulate about this, but it's an issue that arose for me in therapy as being connected to a lot of other things and... ack. ::hugs::