Have I badly damaged my skin?

I've been feeling really awful lately because I realized that I've received more UV light in 2009 than I have in any other year of my life. I didn't have so much UV exposure before that, and would only get sun burnt every few years (but never when I was a small child, and never on my face). In 2009 I perhaps got about an average of 30-45 minutes of sun between noon and 3 pm (and an hour outside of those hours, would that matter?), February through to mid-December (although less after that, except getting a bad sunburn on my shoulders on Boxing Day). I've now become an obsessive user of sunscreen, but still I worry that I may have damaged my skin permanently. I get scared that if I don't get skin cancer, I'll get terrible wrinkles when I'm 25 (although I have quite oily acne-prone skin, which I've heard ages more gracefully). If I keep using sunscreen whenever I am outside from now on (I'm 17), will the UV I've had last year only add up to a marginal effect in the long run? This has been badly upsetting me for the past couple of weeks, I would very much appreciate an answer. I'll be happy to provide more information if I need to be more specific. Thank you for your attention.