your not ugly at all ! I'm kinda that way tho if a man I like or I think is cute looks at me I look down at the floor or look away .. I don't want to be caught looking at them LOL .. I think that's what it is to .. maybe they like you !
Heck no, you are probably not ugly in their eyes. Most guys do this because they think a girl is pretty and they don't want her to catch them looking at her...they think it is stalker/creeper ish if the girl catches them looking at her, especially if she is pretty and she knows it. I even find myself doing this once in a while even though I should be able to control it...sometimes I just see a girl that is too damn beautiful too look at!