Coughing up fluid

Hello!
So I've been coughing up a lot of fluid and have a persistent almost ticklish feeling in my chest. It's really weird as I've had no fever's and can still go to class, go on runs etc perfectly fine. I'm just coughing up a load of fluid! Has anyone else had this problem? I've asked my cf team and they just said I should go on Iv's, which I will. But that's literally their answer to everything. If I came in with a sore knee I'd probably end up on Iv's! I would just like to know what's going on!! Has anyone else had this problem?