S.W.
I would say this is a very common problem after having a baby. Men and women just don't understand each other on this level. I'm not sure if you are breastfeeding, while being way superior for the health of the baby, it can hormonally reduce your sex drive. Also, taking care of a child is a 2 or more person job. Women will always be biologically set up to be the care takers. We use to live in tribes where we had other women helping us. Now we are isolated. The men use to be out hunting and gathering, but since they no longer do that, they need to be helping us. Many times they feel that taking care of the kid is our job because they make most of the money. That argument just doesn't fly in my house. We need help! Communication about your clear expectations is key. Don't expect him to see you stressed out and know to jump in and help you. Men don't get it and they certainly can't read our minds.
Also, get involved with other mothers. There are many ways to meet them. Email lists and playgroups such as Moms Club are good place to start. If you don't bond there, maybe you can find a friend or family member to spend time with . It's nice if they also have kids because you can take turns helping each other out.
Your relationship does change when you have a child. It's normal and to be expected. Your definition of love and what you need changes too. That's why communication is so important. If you can't do it without a third party, you might want to get a counselor.