I would suggest wearing more often gradually, kind of like "testing the waters before jumping into the deep end", eventually you will realize it isn't that big of a deal and it is the LAST thing on most peoples minds.
The only people constantly looking to see if someone is wearing a diaper is probably somebody in our community (whether they are registered on this site, others, or dont know why they have a fascination with diapers).
I don't often wear a diaper outside of the house, but when I do my Mom is the only one saying anything, I have never even got looked at weird by anybody else.
Of course the key to discretion is having a good enough diaper (if you plan to use it) so that it doesn't leak; if a leak happens that will be WAY more obvious than a thick diaper, and also layering; people can guess all they want, but just about nobody is gonna announce "HEY I THINK THIS GUY IS WEARING A DIAPER", unless said person knows you and is a major @Hole.
Most people are considerate and would just assume you have a medical need and not even say anything; that I'd IF they do notice, but again it is the last thing on just about everybody's mind.