It seems that you are doing okay in your interviews, if you've already been accepted to two programs. That's hopeful. However, you've also been rejected/WLed at a few, so there may be room for improvement, barring anything else that might be hindering your app.
Doing well in an interview is all about preparation...as in, be prepared for ANY question the interviewers could ask you. Obviously, you can't know everything they could ask, but you can anticipate 85-90% of their questions just by looking at your application from their perspective. For example, be able to explain how any EC or work experience listed in your app applies to the practice of medicine, or your success as a medical school student, or some such. Look for red flags, too, and be able to address those convincingly without being defensive. Come up with a cohesive story about your life that shows how everything you've done and experienced thus far contributes to your ability to be a great physician.
Write down potential questions -- it will be a long list! -- and then compose answers to them in paragraph form, condense those paragraphs into bullet points, transcribe your bullet points onto notecards with the corresponding questions written at the top, and study those notecards as if you were preparing for a test. (To help with nerves, I googled the scariest, the most intimidating male face I could find, made it fill up my whole computer screen, and talked directly into its eyes. It really helped!)
Check the Interview section of SDN for the school where you'll be interviewing. That'll help you get a feel for the kinds of questions the interviewers are likely to focus on. For example, AZCOM really loves the weird, off-the-wall stuff as in "why is there fuzz on a tennis ball?" If you don't want to have to answer that on the fly, google it ahead of time and be prepared!
Seriously, this kind of preparation takes tons of time at first, but eventually, you'll find that your bullet points for seemingly unrelated questions really come down to maybe a dozen or so "talking points" that you can pretty much use for any question they ask you. With practice, those talking points will be the well from which you draw during your interview, building your confidence and reducing the tendency to ramble. Another trick, it's common for interviewers to ask behavioral questions like: Describe a time when you overcame a significant challenge, or resolved a conflict, or What was your most memorable shadowing experience? or .... Take some time to brainstorm those potential questions and COME UP WITH STORIES! It basically comes down to having stories that show your leadership, compassion, difficulties you've overcome, conflicts resolved, an ethical dilemma you dealt with, a significant shadowing/clinical experience.... think that pretty much covers the bases. You'll want to have those stories prepped and ready to go. Maybe you have one story that covers everything, that would make it even easier! You'll find that, armed with a handful of stories, you'll be able to answer just about any such question without having to scan your memory bank on the spot and possibly drawing a blank.
Hopefully, this will help you. I paid for a few sessions with a professional interview coach, and these are just a few of the points we covered. I also practiced obsessively over weeks and weeks, which was a lot of work and which you may not have time/inclination for this late in the game, but I can tell you that all the preparation really boosted my confidence and enabled me to slam-dunk all of my interviews (like, I could see it in my interviewers' faces kind of slam-dunk. I attended 4 interviews and received 4 acceptances). If you lack confidence thinking on the spot, as I was, or suffer from nerves, then this kind of preparation will save you.
Good luck!
