he wants to work on the relationship and see if it can improve.
I'm afraid I tend to agree with other posters saying there's a possibility this is a warm-up to leaving you for someone else while convincing himself he is a decent guy who 'did the right thing' by trying to 'work on' the relationship first. However, he could also being honest that he is feeling disconnected and does want to work on repairing the relationship.
A good strategy to get a closer to the truth of the matter is to treat his words with absolute seriousness and ask him to clarify for you how he is feeling and what he wants.
Sit him down when you are both calm and say that you want to work on things, but you feel unsure about what work he feels needs to be done.
Ask him when exactly he started feeling more distant from you. Were there things you did or said that annoyed him or he found hurtful? Is he feeling less attracted to your post-baby body? Has he found you less willing to accommodate him now that you have a baby to look after too? You really want to know if you have 'gone wrong' somewhere in your actions in his eyes.
The important thing to keep front of mind as you're asking these questions that you're gathering as much information as possible. Stay outwardly really calm and neutral throughout the discussion even if he says things that make you feel upset inside – just remain curious about where he thinks things might have gone wrong – but don't take ANYTHING he says as necessarily objectively true/right or meaning anything about who you are or how you 'should' be. The calmer you can stay, the more information he is likely to reveal about his thinking.
For example, if he says "To be honest I'm not as attracted to your body now and feel like you're not making an effort to look good for me", I know this will feel hurtful and you may want to yell at him "I had a baby 7 months ago for fuck's sake, do you really expect me to be back to my old body already" but what you need to say is, "Okay, thanks for being honest with me about that. Are there any other things about me that have made you feel more distant from me?" KEEP YOUR POWDER DRY. The time for processing – thinking closely about whether his feelings and thoughts are fair and based in reality or unfair/excuses and weighing them up against your own feelings and thoughts will come later. Right now, you are gathering information, you are not trying to solve anything, make any commitments to change, not judging yourself. You're just really digging into finding out what he actually thinks and how he feels, even if those thoughts and feelings are not complimentary to you or not easy to hear.
Once he's not saying anything new about you and what may be displeasing him about you, move onto him. He says he wants to 'work on the relationship' and he's told you the things he thinks you need to work on – so what does he think he needs to work on? Has he been struggling with the demands of parenthood and feels like he can't keep up so has been too tired to make an effort to connect with you? Did he stop sharing his honest feelings with you (this may well be the case if he has just told you unexpected things, like he isn't attracted to you any more) and if so why? Has he been avoiding being at home because parenthood is stressful? How does he see himself as having contributed to the distance between you? Listen carefully to what he says, and think about whether he is taking any responsibility for the distance between you or whether he is making out that all of the problems come from you and can only be fixed by you. He may also seem very vague about what the 'problems' actually are in his mind and be unable to name what he thinks needs to change.
Once all his feelings and thoughts are out in the open, you say to him, okay, thank you for sharing all that with me. I'm going to go away and have a think about what you've said.
Then go away and do that. Think about whether YOU feel his expectations of how you look, act and are fair and based in reality. Whether he is taking any responsibility for the distance in the relationship and showing a willingness to put effort in to make changes himself or support you to make changes (eg look after the baby four times a week for a couple of hours so you can go to the gym or a salon - this is only if YOU want to do that, of course). Whether he even knows what the 'problem' is and how to fix it.
If you feel that he is largely placing you as the 'cause of the problems', doesn't even really know what the 'problem' is or is unwilling to make any changes himself to support what he wants you to do to fix the problems, these are a major red flags and a good sign that something else is going on. This is a clue to share what's going on with someone you trust (a good friend, your mum or even a therapist) to reality-check yourself.