how to use my body/language to say "No"? Am I not saying it enough perhaps?

Today at work I lifted a bottle of milk and three men nearby talking put their heads down and walked away.

Earlier a guy was moving to suggest he was trying to get my attention, I know he has a girlfriend and turned to the side a bit away from him, then a number of young guys were gathered near me~ I felt like a bone between dogs so I walked away~ when I came back the first guy began to walk past me again~ I "cold stared" and he walked past again, so I asked "[His Name], is it that time again?" [a term used in the past when I was harassed] he said "getting there" looking at his watch, then was fussing over a machine, I went back to reading my coffee book to ignore him.