typically it can take a healthy couple up to a year before they are able to conceive, and that is if there weren't issues such as prior hormonal birth control use, irregularity, etc. You are still very young, and it is possible that your body is just not ready. I suggest to chart your cycles, learn when you ovulate and go from there. There are some great resources available online.
Ovulation Calendar - Free to Use
Otherwise, just be patient and dont stress, as this will make it more difficult to conceive. It is hard to become pregnant, there is only a small amount of time where it is really absolutely possible. good luck.