Sizing is a miles may vary scenario to me. Depending on the body type, frame, build etc what is identical for many may be off for self. A professional fit can minimize the time to figure this out on our own. It took me a week or so I'd say of measuring and comparing bras when trying them on the next day and going no that didn't work but these did and meausring again until i feel i found my happy ground in sizing and so far it's worked well.
I also started wearing bras as a teen. What was a very innocent curiosity turned in to an interest and minor crossdressing as I got curious about other things. That abruptly stopped years later after an incident with an ex. Like others, who knew that the things back then would be a crystal ball of sorts of things to come later as we ended up growing breasts to fill the bras that we for who knows why enjoyed wearing.
I'm glad you decided to join and chime in on the conversations and add your experiences. If theres questions, areas of help needed, or general insights, always feel free to we're all here to happily support those who need support