Unsure...

Are pregnancy tests actually accurate? I'm about to turn 17 in a week and my periods have been late 3 months in a row now. They haven't been as heavy and I've been way more moodier then I've ever been before! I've taken 2 home tests and even gone to the doctors and it's been negative every time but I just have this gut feeling that I am pregnant or something's wrong. I know I should stop being so paranoid but I'm really excited about having children in the future and if there is something wrong I'm going to be heart broken