Kayla,
It does get easier to purchase the clothing you like with time. I remember the first time I went to the store to purchase panties for myself, I was probably 13 or 14. I rode my bike to the store. I was so nervous that I actually passed out on the sidewalk in front of the store. I ended up not buying them that day and had to ride home and explain to my parents how I had cut my face up.
I still remember the moment when I stopped being nervous about buying panties for myself, I was 35 years old. I was shopping at Frederick's for the third time in a month. The same girl assisted me each time. On my third trip she stopped asking what colours "she" liked and asked me what colours "you" liked. At that moment I realized that it's ok for me to wear whatever I want, and the people in the stores don't care who it's for as long as they are selling something. I now I've full time as a woman and don't own a single piece of male clothing.
I know that you still live with your parents, and you need to be a little more discreet. Hang in there and know that eventually you will be out on your own and free to live the way that is right for you. Try not to think of this time as a restriction on the real you, but think of your future as a goal that you can achieve.