I've never had chicken pox, what does this mean?

Over the years I've seen all my friends have chicken pox or tell me about them. I asked my mum and she said I'd never had them and I always found it quite strange. I would have thought by my age I would have had them (13) If I never have chicken pox, would there be a problem. Also would there be a problem if I got them when I was an adult or something