If I were you I would go and get tested. It just saves having to do it later and I everything is fine it will put your mind at rest. I am 27yo and was the same as you. I got my period when I was 12 but it was never regular and for a long time I was having unprotected sex with my ex husband. Not really trying for a baby but not doing anything to prevent it and it never happened. Now I am with a new partner and trying desperately to have a baby so I went to get things checked out and it turns out I have cysts on my ovaries and am not ovulating properly. The best time to have a blood test to test for ovulation is about 1wk before your period is due but if you have irregular cycles that could be hard to judge. Just go to the doctor and talk to them about it. They will put you on the right track. If you do find out something is wrong at least you'll be prepared for it and will be able to do something about it to give yourself the best possible chance when you do want to start trying.
Sorry to go on and on but I just don't like to think of anyone else going through the heartache of being told they may never have children.
Good luck!