Interview nerves...

So I'm a newer grad with a little over six months of experience and I have three interviews lined up in the next two weeks.

Surprisingly enough I have never had issues getting interviews, it's always been the interview itself that I'm bad with.

As a new grad I went on five interviews before receiving my only offer. I don't really know what to do to become better. I prepare questions and answers before and practice. I look up all the information I can about the hospitals. And I even dress the part and bring all necessary materials.

I seem to get my words twisted and tangled when I speak and if they ask me a question I did not prepare for I'm completely stunned and say the most ridiculous things.

I feel like I missed out on such great opportunities with my previous interviews and I want to nail all three of the ones I have coming up so I can work on advancing my career.

Any advice for people who seem to have interview jitters/nerves?