Rib graft nose surgery: I feel like I'm suffocating as I'm not getting enough air—how can I fix this?

Hi! I had septal reconstruction with rib graft one month ago and since then I feel that I don't breath enough air especially when I lay down to sleep. After this happens I start to yawn, suffocate and have rapid heartbeat. It first happened the first days after surgery, then I felt ok and after one month the suffocating feeling came back. What should I do? My doctor told me everything went fine with the surgery.