please help

I have a 2 year old cat who has just had kittens.. this is her first litter and she had 3 I passed during birth and the other 2 were born kicking and screaming! It has been one week to the day that they were born.. Mom has been doing a great job taking care of them but just a few hours ago the baby started crying .. and not the normal whimper cry I expect from them no this was a scream!  mom rushed in and I took a look with her... the baby is meowing and meowing but after every meow it sounds like he has a vibration during inhale... he was breathing kinda heavy but not crazy and he just continued to cry and cry and cry I listened and it almost sounds like croup when he inhales though. nothing soothed him I tried to have him nurse he would suckle and then let go and cry... he is now sleeping with his sister but I am scared I don't want to lose him.... can someone please give me some advice!

Have you possibility to contact a vet? Preferably a vet knowleable with cats.

May be beginning for pneumonia.

*vibes!*

I am going to call today and see what they say ... this morning he seems a little bit better but I am still nervous because his breathing isn't not like his sisters.  I will keep you posted!!