There are likely many photo albums of you two. When you miss your boyfriend, those pictures can help. It will bring back memories of your time together.
If you're missing your guy and feeling lonely, take some selfies and be silly. Reaching out and sending a picture for him to view might sometimes put you at peace. Just thinking about how his eyes would light up when he sees that picture will make you grin.
Girlfriends appreciate wearing their boyfriends' loose, soft clothes. It feels like a partner is there. You probably have some of his sweaters and t-shirts in the corner. Wear one and feel him near. Though corny, it works.
It doesn't have to be your favorite movie, but it may be his. Watching it can bring you closer to him. Watch the movie with popcorn on your couch. Understand his obsession.