I can certainly relate. So many times I went to a store determined and chickened out.. Especially difficult when there's lots of people, many with kids. You kinda have to figure out when there's going to be less people.
Recently, I had the greatest experience. Wasn't even looking for it. I was on Harry Hines (an area in Dallas with lot's of warehouses/wholesalers), looking for something unrelated, when I saw a women's clothing display at one and a dress that was just divine. I stopped, went in, there was this lady. I asked about the dress up front, and said "the problem is I'm not sure what size.. you see, it's for me.. " she was VERY supportive, helped me look, it just wasn't gonna be available my size, but she went further, asked about my likes, wants, I ended up trying 10-15 different things and bought a pair of shoes, some skinny jeans that are to die for, two skirts, a blouse, a bracelet.. I still get goosebumps.
Since then, I've been in 2 or 3 other places when there's not a lot of people, and I have had the nerve to ask for help. I've not yet been hurt. I'm sure it will happen at some point or another, but the liberating feeling to be able to just go shopping and TALK to someone ("does this make me look fat?").. It's definitely worth it!