I know this is not the policy line, but my feeling is that he's just lazy!
OK, now that I got that out of the way... Here are my two cents on the topic.
There are many reasons physical and psychological that he may have a reduced sex drive. It's worth talking to a doctor, but you have to talk to each other first.
It wasn't clear to me how often you have sex - did you say that it's been six weeks?
One thing that you need to talk about is what frequency of having sex would be acceptable for both of you - daily, weekly, monthly, etc.
Many people fall into the trap of thinking that sex just happens, but that's not the case. When you first meet, you automatically take the time and spend the energy because your 'courting' so to speak. When you're in a long term relationship, it takes time and effort - we tend to start making other priorities and our relationships suffer as a result...
Maybe you guys could commit to having a sex night once per week where you turn off the TV and go to bed together at 8 (or when ever you get the kids to bed). As a matter of fact just turning off the TV for a few days can do wonders for your life - sex and other... Head out for a walk - get some other physical exercise. Exercise gives you more energy!
He needs to understand that sex is important to you - it's sounds life you're a bit afraid to tell him what your needs are. I believe that a relationship is a partnership and that both partners deserve to have to their needs met - tit for tat. It doesn't mean that you have to sacrifice everything for him or him for you, but you do need to meet in the middle.
Spend some time thinking about your sexual needs and what would make you happy, make a list, write it down. Have him do the same and then get together (outside of the bedroom) and go over your lists. Sign a contract with one another...
We once knew a man who created a new relationship agreement with his wife every year on their anniversary and they both signed it and had it witnessed - They have been happily married for more than 30 years.
Maybe you guys can create a "hot sex" agreement and both commit to it for the next year.
Think outside the box! The important thing to remember is that you have to work together on this... Dont' be a winer... Don't make him the bad guy... But do express your needs...And expect to get them met...