It's not abnormal for it to take a year or more to conceive, so don't worry just yet. The main thing you probably need to do is relax. Stress, diet, too much exercise, along with other factors can change your menstrual cycle and make it irregular.
Also, go online and look up other ways to improve your and your partner's fertility, including not having sex too much (depletes sperm count), wearing boxers, relaxation, etc.
If you are worried, go see your OBGYN for a check-up.