I'm 24 n have no asthma before. went to a doctor after 4 days of cough+mucus. he concluded that i've asthma. i'm needing a second opinion. thanks.?

More testing needed: You can have cough-variant asthma or allergy-induced asthma. You should see an allergist or pulmonologist. They can do a lung function test and test you for allergies.

Could be right: That doctor may be right especially if he gave you a bronchodilator like albuterol & it made you feel better right away. Asthma is a chronic disease with periodic episodes when breathing gets a lot worse. Most physicians refrain from making a diagnosis of asthma without 3 such episodes. So go see an allergist, pulmonologist or primary care doctor for a lung function test & a 2nd opinion. Good luck.

Maybe: Asthma, by definition, is recurrent episodes of wheezing, cough, shortness of breath, etc. If this is the very first time you have had these symptoms, you might have asthma but would only make diagnosis if/when you have another episode. If you never have another episode, then you don't have asthma.