Heh, if the wind hits me wrong I get an erection. I'm 31, been married for 5 years, and I'm more horny now than ever. If you are stressed out that might be a cause. If you aren't stressed, you might want to see a doctor.
This has always been me too, but lately I find I really don't care about sex. It's starting to cause problems in my relationship. I am very stressed right now, but I think I might go see a doc too.