I think he is a bit sufferrig this due to lower confidence you need to do some efforts in building his confidence by appreciating him with what he is doing in daily activities and show or tell him that no body would bother by what he is doing in social, I mean if he is with you then you need to be look beautiful and he also must be well dressed and look smart. see these are very small things but affects a lot in confidence. And make him feel that he is good enough and it doesnt matter much when you are with your girlfriend and enjoying life.