Hi, I Am 18 Years Old And Have Been On

Hi, I am 18 years old and have been on birth control since I was about 14 due to excessive cramping and heavy bleeding (my periods were always on time even before birth control, like clockwork). After trying about 4 different pills I decided to get off of birth control July of 2013. Since being off of birth control I had a period 5 months apart and then 4 then 2 and so on. Now my periods are just about back on the 28 day cycle give or take a week. However, what I'm worried about is my husband and I have been having unprotected sex for the entire almost year and a half I've been off of birth control and I'm still not pregnant. Is that something I should be concerned about? I'm starting to get worried I have something wrong with me. Is it normal since "technically" I've only had about 5 periods within the last year and a half? Please let me know!! Thank you so much.