Its very much possible that you have one of several conditions which can effect a females fertility one of the big ones is Polycystic Ovarian Syndrome (which is treatable). From the sounds of things, you are not ovulating thus not dropping an egg that can be fertilized (which isn't uncommon) if you are over weight lousing weight can help (though not always).
Getting an appointment with a specialist would be the best option (though 11 years and you are only now starting to worry - makes me wonder why you've not brought this up to you PCP already or even your GYN).
Having normal periods is no indication that you are ovulating, you can have regular clock work periods and not ovulate at all, thus you have next to 0 chance of getting pregnant if you are not ovulating (some women do need medical help to ovulate because they just can't do it on their own - which also tends to mean needed medical help to keep a pregnancy going once it starts in many cases).
Other things that can interfere with implantation is high stress because it tells the body that its not a safe environment to start a new life - so if you are stressing over not having a child you might well be causing the issue (or not).
Luck!
I'm sorry! We had a hard time getting pregnant, too, and it was very emotionally difficult!
Without seeing a doctor for blood tests it's hard to say what's wrong. You can always focus on increasing your overall level of health. Dietary issues, adequate sleep and stress management are all associated with improvements in fertility. If you're overweight, losing weight can help your fertility to return. Do you have any suspicions about what the issue might be? Are your periods normal? Do they come on a regular schedule?