Am I having a panic attack? I can't breathe?

I'm 16 and I suffer from generalized anxiety disorder as well as bulimia. Yesterday I abused the prescription drug Vyvanse (but I only took 50mg) and I ate only 370 calories. All day yesterday I was sweating extremely bad and jittery. Near the time I went to bed I started yawning a lot and realized that I felt like I couldn't fill my lungs. I thought it would go away. Today it's still difficult to get a deep breath. I know that this drug can cause panic and that as a person with GAD it was probably stupid to do. But I've taken Vyvanse before with no problem ( I take it because it greatly helps my social anxiety) Am I having a panic attack?