What Causes Excessive Yawning?

I have been experiencing excessive yawning, even after getting 7-8 hours of sleep. It sometimes feels like the only way to get a satisfying breath, so my yawning is sometimes triggered by my need to breath better. I started a new job recently, so anxiety seems like a reasonable potential cause, but I also suffer from allergies. Which is the more likely cause? I m sure my boss thinks I m incredibly bored with my job, so my excessive yawning is a little concerning to me.