I kinda look young for my age; this invites so many creeps to my job. What can I do to stop this?

I (18F) look pretty young for my age. I know that 18 is young, but compared to how I physically look, most people assume that I am 13 - 14 years old (or sometimes younger). It doesn’t help that I am short (5’0) too with a baby face. Anyway, I work at the customer service help desk at my local grocery. Working at the desk is fine, but sometimes, creeps come in. They keep staring at me as they walk past the registers, and a few have come up to speak to me.

Some comments I have heard: “You’re pretty cute, miss. Smile more!” or “I bet you’ll make anyone happy.” Usually, I just ignore their comments. Recently though, there was this one couple that came up to the desk to return something. The woman kept staring at my shirt/name tag. She said something to her husband, before turning to me saying how it’s great that I’m young, and that my womb was ‘blossoming.’ I was so disgusted and creeped out; I told my manager, but he said that he couldn’t do anything as they didn’t do anything physically to me.

Since then, I’ve been having a hard time going to work. Maybe it’s my anxiety. I was SA’D a year ago, so that disgusting feeling I had back then is back. I can’t leave this job as I need the money (I left my parents’ home to live with my grandmother who doesn’t work). I thought about getting an on campus job at my university, but most of those positions are already filled. What can I do to protect myself? How can I stop this?