I hear you Andi! When this happened to me, the doctors figured out that my IGE level was extremely high & they suspected I had ABPA (Aspergillus aka. mold, in the lungs) It's not something you can test for but because of my high IGE level they put me on an anti fungal & steroids & it works wonders! Also I agree with Iamqueenofeverthing, you could have allergies. I would see an allergist who can test you!
You could have other things wrong with you other than CF.
Also, I agree with everyone who says to exercise! It's so hard to get in that mind set everyday but TRUST ME, working out does wonders for your lungs! Even if you don't see it right away!
Walking the dog is good though! Keep that up. I walk my dog 5 times a week then i go to a spin class or get on an elliptical! Anything to make you feel like you are working those lungs! I hope things get better soon!
Keep us posted! xoxo