First, dear, I certainly understand your fears! God knows, I've been there too. And I survived -- much to my surprise.
I agree with most of the responses: From my experience, very few clerks care. That said, you could run into one of the bozos who get their jollies by hassling customers. It has happened to me once or twice. In that case, look at them like they're an idiot, snort, and say that it's for your mother/wife/sister/daughter --
"Of course!"A bigger risk is running into someone you know while waiting in line. Someone who's nosey and will ask why you're getting that stuff. I don't mean to scare you, but it can happen. The best defense is to pick a distant store, and/or go when the store isn't crowded. Or, if you don't want to see that person ever again, tell them you have lice.

It's important that you don't act scared or fearful. But it's okay to act frazzled or overwhelmed or confused. For example, I often adopt an attitude like,
Good God! I had no idea there was so much STUFF! She just told me to get hair remover. Why didn't she tell me what brand, blast it! Clerks respond well to that.
However, I have to warn you about one thing: pacing around a store for 40 minutes could be a problem. That behavior might put store security on alert. If you have to do that, better leave and come back another day. Or first surf the web to figure out what to get.