Need Advice!

I've been having unprotected intercourse for about a year but activly trying to conceive for about 3 months using opk. I've never had an std, my cycles are very regular. Everything is pretty normal. My flows are not heavy. My dr said I need to try for another year before they will do anything. I'm 22. I've been married about a year and a half. I need some advice! Why am I not getting pregnant!