My S.O. doesn't seem interested in sex anymore.

Charlette
My significant other and I recently moved in together. We have been dateing for about a year, and he recently got a job as a store manager. Before we moved in together we would have sex for hours and lay in bed and talk all day. Now we barley have sex once a week and it lasts for maybe 5 minuets. And as soon as it's done he goes in his computor or downstairs to watch tv. 
Is this normal for couples who move in together? Am I doing something wrong? Is there something I can do to make him want me again? 
Any help would be great!