Try using Ayre,my sleep Dr recomended it for me, spread a little inside your nostrils before you put your mask on. Breathright strips may work for you also. Usually the problem in not enough moisture, move your setting up one notch a night and see if you can get it to where you are not as conjested. I have mine set half way and it works for me. Also you may ge****er in the tube, try to keep it under the covers, warm water coming from the chamber and going thru the tube in a cold room creates this sometimes. I use this http://www.sleeprestfully.com/hybernite.asp
and it works great, no more keeping the tube under the covers, my wife uses it also and is able to keep the mask on all night now. I've been on CPAP for three years. Hang in there, you'll get it right.
Edit: I also use the pillows there great I switched masks like 4 times in the begining, till I got the right one for me, you should not have to pay for a new mask every time as long as it's in 30 days. You can use a Neti Pot also to relieve congestion, If you use it regulary this may be all you need. Get the squeeze bottle type, not the tea pot style.