Can't Climax

Hey y'all,
I still consider myself fairly new to sex.  I've only ever had sex with my current boyfriend but we have been at it now for a year and a half.  
I seem to only be able to climax when he goes down on me and still it doesn't happen every time because of probably a million reasons (mostly impatience).  It's not a huge problem I guess but I would like to be able to climax with him, together.  I'd also like to climax MORE.
Thoughts?  Suggestions?
Is this common or am I alone?