This is a very common course. It is not bad luck that this happens, but rather airways that are not controlled and waiting for an event to trigger them. I would discuss preventative therapy with your doctor. There are thousands of people with asthma on preventative inhaled steroids to prevent exactly what you are describing. The fact that the episodes have increased in severity makes this even more important to consider.
Every asthmatic should have an Action Plan to monitor and adjust the doses of his medication, depending on symptoms and peak flow readings. Typically when peak flow drops to 80% of normal, the dose of inhaled steroids is doubled and albuterol inhaler used as needed. See:
http://www.vh.org/adult/provider/internalmedicine/AsthmaIM/comp1/AssessmentB.html
Asthma Education: Interactive Guidelines: Component 1: Measures of Assessment and Diagnosis of Asthma
Part B: Periodic Assessment and Monitoring: Essential for Asthma Management
Michael W. Peterson, M.D.
Excerpt:
"Every patient with asthma should be taught to recognize symptom patterns that indicate inadequate asthma control (see figure 1-8, and Component 4). Symptom monitoring should be used as a means to determine the need for intervention, including additional medication, in the context of an action plan (see figure 4-5)."