You cannot ever smoke again. Asthma is just the beginning of lung damage caused by smoking. After asthma comes bronchitis, loss of lung capacity, then emphysema and lung cancer.
They are called cancer sticks for good reason. I know it is hard to quit, but you must if you value your life.
As it is, you will be plagued with lung problems for the rest of your life. Don't let your lung problems get worse by continued smoking.