Tamika... Learn learn learn.
The interview and hiring process is sometimes a journey! It's a skill that can be practiced and improved upon. Every interview you go to should make you better at the next one.. I'm sure there might have been a couple questions on your last interview that you were unprepared for.. OK, so next time, you'll have your answers to those questions rehearsed and down pat! After a couple interviews the nervousness decreases, but the adrenaline is always there, making you sit a little straighter, focusing your attention! Just keep practicing.
And from your first encounter with HR... I hope you called and confirmed on the second interview, and from all future interviews. Should you have to do this? Prob not, but whether HR screws you, or it's your own mistake, the results are the same.
So, leave nothing for chance, maximize every opportunity, and keep working at it... It's a hard job, this business of getting a job!
Bill