Fertility

Hello , I’m 20 years old and I’m completely clueless right now .... Me & my bf have been trying to get pregnant since January and have no luck , every single time he ejaculates in me we have a pregnancy scare but no actual pregnancy , like every single time my period comes late by almost a week and then randomly pops up. Does this mean I cannot have children ? We’ve been humping like dogs and still nothing ... Could it be something with him ? I’m just discouraged & looking for answers .....