This is a very common problem. And there are a lot of reasons why it occurs. First, if you have been breastfeeding, your hormones are actually suppressing it a bit. Add that to the simple fact that you're TIRED and stressed, and that alone is enough to make you collapse in bed every night with a desire to do nothing except SLEEP. And if you work outside your home, (or stay at home with your child, for that matter) you are additionally stressed. I read once that every baby increases your workload by 40%. That sounds a little on the skimpy side, if you ask me!!
As for advice, I have a couple of helpful hints. First, make romance a priority. Go out on a "DATE", dinner, dancing, a movie, whatever, but try and remember why it was that you fell in love with that guy in the first place. In other words, THINK about it.
Hire a sitter or send the baby to grandma's for the night. Take a weekend away, even if it's at the Holiday Inn two miles down the road.
Sometimes after a birth, sex can be painful--that doesn't do much for the libido. Talk to your health care provider if that's the case. Lubricants are a wonderful thing. I recommend Astroglide for my patients.
And now, a word to the spouses out there--Wine, dine and romance the lady in your life! Make her feel as special as she truly is!!! Think back to your dating days, and recreate those feelings!! Make an effort to be tender and kind; YOU make the sitter arrangements. Sweep her off her feet.
Remember you were a COUPLE before you were parents. You will be a COUPLE when your parenting duties are NOT the most central part of your lives together, so nurture that part of your relationship. It takes WORK--but it is well worth the effort.