Children laugh when in discomfort when they have been told repeatedly not to cry,to shut up, to suck up their pain, and things like - give you something to cry for.

children don't learn to cover pain without having their pain discounted and ridiculed through emotional and or physical or sexual abuse.

You have not abused your baby so there is no reason for him to cover his pain and discomfort.

You know the different between his crys of hunger vs his laughter in eating an enjoyable meal right? same thing.

if you could not understand when he is happy versus sad you would not be able to feed him, rock him, cloth him appropiately, put him to bed and so on.

When you have a baby there is no in between area that depends on what the activity is.

Babies natually and instinctively expresses themselves the same ways each and every time no matter what the activity - they frown, cry, pout and whimper when sad and uncomfortable and gurgle, giggle and smile and laugh when happy and comfortable. and a parent naturally known the difference just from being around their child and interacting with that child.

the only time any child no matter what age covers their feelings is after they have been shown through abusive ways - hitting, being yelled at, ridiculed and humiliated - that showing their emotions is dangerious.

Since you are still uncomfortable with interacting with your baby you might want to locate parenting classes through mental health agencies and planned parenthood agencies that can help you bond and understand your baby's needs and the differences between his emotions.