Wow... So I hope you all don't mind a man's point of view... There are a lot of reasons that this could be happening... I have my experience with long distance, as I am currently long distance and I have spent 5 years in the U.S. Army, with all of my training, three years in Germany and two deployments (currently in my second), I have plenty of experience with long distance. I will try to hit all of my reasons without being too much of a devil's advocate here... since no one wants that.

To get the worst out of the way, you haven't been dating very long, how well do you know him, and how well do you know what happens when he is away for four weeks at a time...? Maybe he isn't as "pent up" as you are. I will stop there.

As Roman put above, past relationships could have forced him into thinking less of sex in general or maybe just in his ability to perform. Was he having sex when he didn't want it? Was he never told that he was good enough when he did do it? Do you let him know (or did his past partners?) how much you enjoy sex with him? I know that with my ex-wife, my sex drive was very low, because during one of our times away I found out she had been faking it with me from the start and it hurt me. Also, there were other issues, cheating, lying, and just generally not feeling loved or cared about. All of those things whether current or in the past can affect his "drive". Although with my current girlfriend my drive is the total opposite, she has a very high drive, and mine has jumped to match because our relationship and trust in one another is so much better.

There could be a physical problem also. Where mental issues can block sex drive, cause premature ejaculation or erectile dysfunction, physical issues are also not to be over looked. Have you tried to Google if sex drive can be a complication or side effect of gull bladder surgery? He could have a hormone problem causing him to have low testosterone and a low sex drive. Does he work out often, lift weights, physically active? All of those can increase testosterone and improve sex drive... Is he overweight, especially around the midsection? Even as few as a couple of inches of belly fat can significantly lower testosterone in the body and cause him to have a lower sex drive... Just a few things to think about. If this continues, there is testing that can be done (and usually covered by health insurance) to find out if there are any physical reasons for a lower sex drive or other associated problems....

Lastly, he could just naturally have a much lower need for sex than you... As that may not be good news, it can be true, although personally I would look to other areas before I left it at this. As in men this is unusual. Men are physically "wired" to need sex. Sex releases hormones that are not released at any other time for a man that cause feelings of closeness. A man's body needs physical release, or otherwise he would likely have "night emissions". Also, not having sex (or being denied sex, although this is not your case) can have a deep emotional impact on a man's psyche, that can cause serious problems in a relationship. I would recommend a book called "For Women Only" by Anne Rice. It gives a very good look into the "typical" (I say typical because every man is different), man's thoughts and emotions that is very close to the mark. I would recommend the set (she also has a "For Men Only" too) to any couple as it is very educational on the mysteries of the opposite sex.

One last tip... testosterone levels are usually highest for a man around 0700 (7 am), so you may want to try to get a little frisky in the morning instead of at night....

Hope I haven't been too much of a downer.... good luck and I hope for the best...