breathing trouble

This probably sounds totally crazy but I'm 6w and I feel like for the last week I can't get as much air in through my nose. I'm not congested or stuffed up- I literally feel like my nasal passages are restricted or narrower. I'm a runner so I'm really in tune with my breathing and I have had to cut my runs much shorter because I feel like I'm suffocating. I'm having to breathe through my mouth when I sleep now to feel like I'm getting adequate air. Has this happened to anyone else or is this something totally unrelated to pregnancy? Thanks!!