Joey bud, you must be a really young guy! I'm guessing as you talk about being 11-13 and saying that you were thinking of telling "your teacher" (only one?) Does your mom know about all this?
OTOH, you are talking about shopping by yourself.
Anyway whatever it may be, you are doing a good job. If you can shop in the guy's section, I will tell you picking up a pair of boxer briefs isn't too hard. I think it helps if you know what you want ahead of time. It took me a little bit to realize where they put things.
Nobody has ever looked at me funny or asked me any kind of weird questions.
--Jay