I get sinus/nasal congestion when i don't use the cpap!

I was happy to see the title of this post, but I see you're talking about overall.

I just started using a BiPAP machine on the 6th of this month. Since my insurance is Medicare, I HAVE to use the machine every day for 4 hours for the next two months or Medicare won't pay for it. My problem is (as it was in the sleep study), I find breathing so much easier with the BiPAP machine on. Literally, when I take the full face mask off sometimes I can't breath - I feel like someone is trying to choke me to death. My sinuses are that bad. The traditional route people tell me to do is use a nettie pot or simple spray, but the only spray I can use is a generic Fluonase or I get a sinus infection. I've always had sinus problems, which is why I didn't going into singing professionally. Is there anything I can do other than wear a Breathe Right strip to keep my sinuses from swelling the minute I take my mask off? (I use a humidifier on level 2) I've been to an ENT before and they said I did not have a deviated septum.