There is only about 7 days during her cycle when she can get pregnant. During that week it is important that you have sex at least every second day. If not, you are relying on luck to have sex on the right days and it can take longer. The average time for women to get pregnant is 3 months. Up to a year is common. After a year you have to see your doctors for a checkup.
Remember to keep it fun and relax. Sex can become very routine and boring when you are trying for a baby.