Hospital diagnosed me with asthma attack, bronchitis, and abdominal aortic aneurism, class today should stay at home while on prednisone for 3 days?

Aneurysm?? If a 19 yo was diagnosed with an aneurysm much more information is needed. You should ask your doctor about the asthma and bronchitis, your ability to go to school depends on how stable you are.
Home. You should clarify your level of activity allowed with your pcp or pulmonolgist that saw you in the hospital they may be able to get you into a supervised exercise program while you start back to normal activity.