It is truley remarkable that there are actually women out there who are sex starved. I feel for you. Heck, I feel with you (trust me). It amazes me that somehow by some weird twist of fate that it seems we end up with people we love, but have very different sexual needs. Just once I wish... well anyway...
To get back to the point - as a guy - I have had this same issue with my wife of 10 years. It got to the point where we had sex maybe once or twice a month - maybe, IF I complained, maybe 3 times. And I am a big fan of all kinds of sex, in fact, intercourse to me is more of "icing on a desert cake after a full meal" - everything else, from oral to you-name-it gets me "going" far faster and better and get horney very easily.
Unfortunetly, what people (counselers, posters on this forum, etc...) will tell you generally does NOT apply to men. Granted I am one man, but I can tell you with much certainty that what is discribed here really only works with women. I hope this does not sound sexists - it really is not meant that way.
What I mean is - men do NOT want to talk about sex - especially to anyone other than our significant other or our right hands

. I am sorry, but we don't. Yes, we may have issues, but these will be buried so deep, by the time they come up, well, it will be far too late.
What worked (more or less so far) with me was the talking, complaining, turning it around on her physcological battle type of stuff. That seems to work on women. I have yet to see it work on men, I don't care how horney or not they are.
Fortunetly, with men - it is normally quite simple to find out what is going on.
I am going to suggest you try something to figure it out. Only a suggestion...
a) It MAY be an issue with him from his past in either a bad encounter, some type of sexual assult, or some change in his body he is worried about. This one we will tackle last, cause it is the hardest, but is the most likely - so it is listed first.
b) He is having an affair. Could be real, could be "virtual", i.e. internet, could be many things. This one is less likely, but harder to prove. We will go through later why it is better to attack this one on the offense, rather than defensivly trying to "catch" him.
c) It is possible his labido is low in general. Also, it could be his attraction for you could be more "sisterly" and thus tougher for him to get past this. This one is least likely unfortunetly, but is rather easy to fix if it is. This pne is the easiest to go through first. When you are "in the mood", what do you do? Am curious, as from what I know, read and hear from guys, 9 times out of 10, the woman waits until they are both in bed, in that boring bedroom, maybe not even naked, and goes right for the "happy" spots on a guy - chest, nipples, pe-is, etc. If this is what you are doing, or anything even close to this - you must stop right away. No guy I have ever met has ever been turned on more than when they were not expecting it or less than when are in the bedroom at exactly 10pm. You want to get him going? When was the last time you walked through the room he was watching TV in naked - or close to naked? Kids? No excuse - get a babysitter. Take the offense position on this one. Get a manicure and pedicure and have them (or do it yourself) paint red or hot pink. Get sexy, think sexy, then... well use your imagination

Yet again, no guy I have ever met have ever, EVER rejected their wife or girlfriend who went on the offense in any other location other than the bedroom. Would love to hear from anyone who has. If they have, then I would worry about b) or a) above.
Quickly, c) does not work - find out his history and such and try to rule out a). I knew a guy who would not have sex with his girlfriend "until they got married" because he was worried about being uncircumsized and her seeing him. I too am uncircumsized and am very proud of it, but many people are not. Mayve he has been abused early in life. Never know.... He HAS to be able to trust you 100% - and I do not mean as a "friend". I mean trust you with his most personal info to maybe get at what is wrong.
I will not go into b) (possible affair) right now. That one requires it's own post, so let's just rule that out until all other options are exausted. Good luck.
Wild1