How can i gain confidence desipite my big nose?

no offence but maybe you just being paranoid? you said the girl gave you dirty looks maybe it was because you were wearing a hooded jacket they have bad reputations now and maybe the girls saw something else in you that they didn't like and you just blamed it on your nose. Even if you did have a "normal" sized nose you would just find sometimes else about you that you don't like, we all do it