1. Give it time because it might just be a phase and you don't want to regret finishing things with him
2. remind yourself all the great things about being with him and that he is a great person etc.
3. Do different things, at about 9 months into a relationship I get bored and usually end up finishing with the guy... go to different places, try new things, don't let yourself get stuck in a rut.
4. Be there for him. Maybe his depression is having an affect on you, making you feel down. Perhaps once it's improved things will go back to normal?
5. Do something special for him...for no reason, i.e. romantic meal, make him a present. Just because. It will be the starting point for a great night.
Hope that helps in some way.