You said your relationship BEFORE the baby was great ... now you just don't care.
I know from personal experience (I have three children ages 16, 12 and 1.5 years old) what you are "feeling" IS normal.
Your body has undergone enormous change ... YOU have undergone enormous change (mentally, emotionally, physically, hormonally, etc) ...
My last baby was born over a year and a half ago, and I am just now getting past the stagnation of the "neutral/numb" stage ... and, I will agree, left unrecognized for WHAT IT IS can definitely be a relationship killer.
So far, from what you have been willing to share, your man seems like a nice enough guy ... you bonded with him initially for some reason ... you will NEVER find perfection in anyone or anything. Does he love his baby? Is he a good father? Is he trying to be attentive and supportive? Or is he abusive or addicted or adulterous? If he is, now THAT is a whole 'nother story.
If you're "just not happy" ... "just not satisfied" ... just not "feeling the luv" right now ... then, please, I ask you to reconsider the entire situation.
My advice is to be patient, wait, and seek to find some sort of common ground with him again (I'd start with that precious baby the two of you created together.)