Are you at a higher risk of a pneumothorax if you have already had one?

Depends... Recurrent pneumothorax depends on the reason behind the first pneumothorax. If this etiology is treated, your risk of a recurrent problem is much lower. See your doctor to discuss your individual case!
Yes. Persons who get one spontaneous pneumothorax (collapsed lung for no apparent reason) are at a higher risk for getting another one later. Some articles say that 25% to 50% of patients will get a second pneumothorax. The majority of the recurrences happen within the first year or two after the previous pneumothorax.
Generally yes. A pneumothorax by trauma is different from spontaneous pneumothorax (sp). Published 5yr first recurrence rates for primary sps are around 20-30+%. For secondary sps, around 40+%. You should discuss with your thoracic surgeon the specifics and reasonable expectations of your pneumothorax. Be well.