Pregnancy

Well I haven't had my period in a little over 2 months and stopped my birth control match 25th and my doc did a pee test and said I wasn't pregnant. But I don't know what else it could be or if I am pregnant why didn't it show up on the pregnancy test. I am very nervous we have been trying for almost 7 months. I lost my first baby when I was 15 now I'm almost 18 and I really hope I'm pregnant...