You've had developed Hanahaki. A disease caused by one-sided love in which the victim coughs out petals. If the infection is untreated, flowers will start to bloom is their lungs, skin, and other organs. The only ways to treat this is if the person returns their feelings, or get it surgically removed. However, if the surgery were to be done, the victim will lose feelings for the person.

You look down at the petal your coughed out in horror. Your chest hurts.