How long does it take to get pregnant

How long should it take for a healthy 25 year old to get pregnant.. I suffer from acid reflux and stomach bacteria I've been having unprotected sex for over 4 years and never once have me and my boyfriend gotten pregnant... I know it's not him cause after we broke up he got a girl pregnant in 1 month.. I've been to the doctor and they have said that I'm completely fine... I've even timed intercourse around the fertile window and never once gotten pregnant.. what should I do i really want a baby before I'm 30