Is this boy showing too much interest?

I am a bit worried about this boy at work. He is very attentive to me and always looks out of the window when I go past at lunchtime and waves, nothing wrong in being polite but, I have seen him waiting for me to go past! He is always saying things like, 'you look nice today' and innocent stuff, but he is making me feel a bit creepy. One of the other girls at work said he has been in trouble for pestering girls before, and I am worried he is becoming a bit obsessed with me? I don't want to get him into trouble, but I feel really uncomfortable around him, like he is studying me all the time? How can I tell when too much is too much?