Really, they will not care. I know it's so terrifying and hard to believe, but it's true. They just want your money, honey.
I used to pull out my cell phone, and when I got near the cash register I would say something like, "OK, I think I got it all....OK, love you."
Now I just shop as a female and it is fine too.
Want a real funny experience? After you are comfortable shopping en femme, buy a box of tampons. Make sure you pick a cashier that is male. Trust me, they will not even look at you. I think it is hilarious.
Great job on the undies. Hardest part is now over for you. Enjoy.
Kristi