Nothing happening.

My fiancé and I have been trying to have a baby for awhile now. Before he deployed and nothing happened. Now that he's back we've been trying for about a month and still nothing. TMI alert, my previous relationships were unprotected and I didn't get pregnant. It makes me feel like something is wrong with me and that I can't get pregnant. The doctor won't do any tests until we've been trying for a year and because I am young. It's just so frustrating and I wish I knew what was wrong. Any advice would be great :)