How do I get the "passion" back in my marriage?

My husband and I recently had a baby, that we are absolutely in love with. But the fun and passion in our marriage just isn't there. Our son is a very demanding baby, so date nights are very rare because we never have a sitter. I just miss having butterflies in my stomach everytime I see my husband, I feel like we are just roommates. Our sex life is suffering, I'm always asking for it, and he's always too tired. He is under a lot of stress from work but don't all guys crave sex ALL the time? I can't help but to think he just doesn't want sex with me, after pregnancy, I just don't have the same body that I had before. I know that he loves me, I just don't feel like I make him happy. I need advice.