premature baby

My boy was delivered at 33 weeks through an emergency section. He had to be resuscitated and has breathing problems 3 weeks on. They are now saying it's not because he's premature anymore and it's something else he has a lot of mucus on his chest that's not helping his breathing and a collapsed lung, they don't know what's causing the mucus but I was told it could be cystic fibrosis but he's been tested and it's not that now he has to have more tests. Has anyone else had this I really need some advice as I'm so scared it could be something serious please help