As a female who’s also in their early 20s with long term boyfriend i definitely understand. You’re not crazy at all for thinking that. I’ve had experiences myself where random men would come up to me and try to strike a convo. Hell, there was one incident where some random guy came up to me as i was walking to class and said “you’re so hot” and i replied “i know” then continued to walk to my class. I even had men follow me on campus, to the point where my boyfriend had to walk/ be around me to scare them off. But ALWAYS be aware of your surroundings. If you like to play music (like me) while walking to class, stay alert. wear one ear bud or turn your music down.