Well, first off, how long has it been since your baby was born? It is not uncommon for there to be a bit of husband vs new baby jealousy for mommy's affections. It's a point of contention in many relationships.
If you are recovered from birth, very seriously, there is a possibility that you just have to make yourself have sex. That sounds awful, but hear me out. Many people (not all), if they don't have sex for awhile, sort of stop wanting it. To get back in the swing of things, it may help to just do your darndest to get into the mood and have sex whenever you can.
If the problem is time (no one knows better than me that babies take a lot of time and energy), agree to come together with your husband at a time when you know (or assume) the baby will be asleep. If the baby happens to be awake at that time, wait until the baby is asleep, but don't give up. Even better, bring your little one to Grandma's for a while if she is near by.
Whatever you do, try not to let the baby be an excuse. "Sorry, honey, the baby kept me up and I'm too tired." If sex vs baby is already a problem, that is nearly guaranteed to make things worse.
I hope that helps you get your sexy groove back. Remember to be open with your feelings. If all else fails, counseling is not a bad idea.