What does it mean when your boyfriend does not give you a birthday present?

That depends on the boyfriend. Some boyfriends are unemployed and can't afford anything. Some are selfish jerks. Some are kind of ditzy and forget. Some don't think that they are close enough with their girlfriend that presents are required. Some actually believe their girlfriends when they say he doesn't have to get them anything. Some have a specific present in mind, but can't get hold of it yet. And there are probably some that were so abused and neglected by their parents as a child that they don't even know what the heck a birthday present is.

I think you may be asking the wrong question. The right question would be: "Why didn't your boyfriend get you a birthday present?" And the right person to ask would be your boyfriend.