cant take deep breaths...

so I am 22 weeks +3 with #3 and I can't take a deep breath.... I am not short of breath when I do things. just sitting down watching a movie I literally can't take a breath deep enough to satisfy me... anyone else going through this or know why it's happening? I am fairly tall so I don't think I'm running out of torso room yet.. I am also very physically active... thanks!