JUS' E-MAIL ME: MY PARTNER WANTS LESS SEX THAN I DO!

My boyfriend and I are both 18. This is my first-everything-relationship, first kiss, sex, exclusivity, etc…We had sex on the second date and would have sex almost every time we would spend time together at night. But that was only twice a week! And even then he normally isn’t interested in going another round when we'd finished. I just feel that something’s wrong. Many nights I make it clear to him that I would like him to come over but he doesn’t want to. Is he too lazy? Should I tell him to stop masturbating?  Did I make things too easy?  Honestly I’d like him to be a bit more aggressive with initiating and I think I’m making it clear, but he isn’t picking it up.  I can’t make sense of this, if you can, please help. 

Have you ever had to deal with this? 

What are your thought?

What advice would you give this person?