Getting over the fear of wearing and changing in public is the hardest thing to do. BUT once you achieve this your brain stops caring who knows.
Some things to remember that can help.
1) the sound of a plastic backed diaper is louder to you for a couple reasons - the first one is that when you put it on at home, the acoustics are different in your house than out in public. SECOND- you can hear it better because you are actively trying to listen. The average person out in public is too engrossed in their smartphone to even notice.
I once went to the grocery store wearing a thick and quite loud diaper under basketball shorts (they do NOTHING to hide the sound). My shirt had gotten stuck in the waistband and I was "exposed" in the back.
No body seemed to notice and if they did, they never said anything to me. When I got home I discovered that my waistband had been showing. At first I was ashamed thinking about how many people probably saw my diaper, but then I realized that I will likely never see any of those people again. So who cares?
2) as to the sound being noticeable back around 2000-2003ish baby diapers stopped being plastic backed and they all went to cloth backed. This made them MUCH quieter. So for the last 20+ years people haven't really associated the sound of a plastic backed diaper with diapers in general. If someone hears your diaper they are not very likely to put it together and will likely think you have a bag or wrapper in your pocket.
3) People in general are quite respectful of a person's medical needs/disabilities. If someone figures out you are wearing, they are very unlikely to say anything. And certainly less likely to say something negative.
Once I was at a laundromat and I needed to change, I went to my car and grabbed a new diaper and my wipes. I walked back in and headed to the bathroom. As I passed by a family the boy said to his mother: "why does that person have a diaper"? The mom was quick to shush her son and I heard her explain that sometimes people have medical issues. When I came out of the bathroom I passed by and the mom mouthed silently to me "sorry". I just told her "no big deal, kids don't know better and you're doing a good job of explaining".
4) It's all in your head. Nobody cares other than your doctor and your family.