Hi , I'm 19 And Haven't Had A Period Since

Hi , I'm 19 and haven't had a period since Aug 25 . I've taken two home pregnancy test and a blood test at the hospital and negative a couple of weeks ago and they were all negative . I have no current conditions or diagnoses . Usually when I'm late it comes after 3-5 days but it's been two months and I really want to know what's going on my doctors office keeps rescheduling my appointment S so it's really nerve racking to me . Is it possible I'm pregnant and my hcg is low or what else could it be .