Been dealing with the same issue myself! One thing that's helped me is to take a moment before answering each question to think about my answer and construct my sentences in my head. It'll look more natural to an interviewer if you take a few seconds to think about what you're going to say, and it'll help you cut down on using filler words when you feel like you're not sure what to say next. I've been making an effort to speak more slowly as well, as I revert more to the teenage girl-talk when I'm speaking quickly. Focusing on slowing my speech helps me sound calmer and lowers the pitch of my voice. I've also been trying to be aware of when the ends of my sentences are ticking up in pitch, making it sound like I'm asking a question rather than making a statement. It's a tough habit to break, but just practicing with a variety of friends/family has been helping a lot! Good luck!