Hi Night Scream,
First of all, Welcome to Susan's.

There's plenty of information available here and even more caring people to help.
It sounds like that since you live with your parents you probably won't be able to receive pacakages. Therefore, unless you invest in a PO Box, you probably won't be able to do much shopping online.
As Shelley pointed out, it is less intimidating to shop for clothes when you have something to tell the sales people (if they ask). Depending on where you shop, you may have some odd looks or inquisitive people, but the more comfortable you are the easier it will be.
Here are 2 tips that may help. First, if you have a close female friend that would be willing to assist you, have her do your shopping (this is what I do for my SO, Rachel). It is best when they have a similar body build to yours and similar tastes; however that is not necessarily imperative. As long as they know what you like and don't like they should be able to do fairly well in selecting items that you will love.

Second, the more information that you have on your sizes the better (this goes for if you have a 'secret shopper' or not). Here's a secret, women's clothes and sizes are possible one of the most convoluted system ever. If you wear a size 12-14 in pant you will probably need a size 6 in underwear. To any sane person that would not make any sense...but somehow this system still exists. When you just start out you probably won't need to much information (undergarment sizes, pant size, shirt size) but as you progress you will find out another hidden truth...women's clothes makers have a sadist way of making sizes. What would be a size 12 in Express pants is a size 10 at Old Navy and 14 at AE.
If you can't find a 'secret shopper', here's another rather timely suggestion. During the holiday season many organizations do "wish trees" (we had them at my Church all the time). Typically, you would receive a card with the individual's age and gender along with the Christmas gift that they would like to receive (usually undergarments, shirts, or perfume). If questioned by the store clerk, just say that you are purchasing the items for an under privileged individual for Christmas (something that we should do anyways, but I digress).
I hope this helps. Good luck with the shopping. And again, welcome to Susan's.

--KyleW