If you get one concussion, are your more likely to get another one?

No;BUT: Repeated brain injury is bad.Our (medical types)awareness of repeated brain injury, i.e. Concussion, is growing.We are becoming more afraid of the consequences of repeated brain injury.

Yes, risk goes up : Yes. It is well proven that if you have had a concussion, your risk of having another goes up. If you have a second concussion, there is also a higher risk for that 2nd one to be more prolonged & have worse symptoms.