Scared to go in public?

I haven't been in public for about 6 months now. I'm 14 and I'm just scared to go in public. Like Walmart and stores like that. I'm a little big (not that much) and when I go to stores like Nike and PINK I feel like the other girls and workers there are judging me and thinking that I shouldn't be there. I feel this way going everywhere. I go to a charter school so it's only there and back. That's the only time I get out the house (I have a huge yard so I'm not inactive) but when I need things or new clothes my mom and grandma sometimes get the wrong thing. Anyone else? How do I get over this? I'm confident in the way I look bc I believe everyone is beautiful but I just can't go in public.