Why can’t I breathe?

Okay so I’ve had a cold for about a week now and it’s been relatively mild. Sore throat for a few days, runny/stuffy nose. Very very minor congestion, almost nothing at all and I did lose my voice. But there is this weird symptom I’ve never experienced. Whenever I’m sitting down, eating or trying to sleep. It’s hard to breathe. Like I’ll breathe in and it feels like my lungs are trying to stop me from taking a breath. My dad has been saying it’s just mucus or congestion in my lungs, but as I said before I really don’t have any congestion. And it’s weird that it’s hard to breathe only when I’m not doing anything. Anyone have any ideas? EDIT I feel 100% when I’m doing stuff, like I could be jumping and running around and I feel great.