We understand the situation you are in but there is nothing to be embarrassed and ashamed of how you are performing at interview. Most of us face such challenges but it can be easily overcome by practice and finding out the root cause.
A self-reflection activity might help you here. Write down situation at last interview, what happened, where you got nervous, why nervousness happened and what you could have done differently to handle the situation more effectively.
Being mindful of the situation and staying in present by focusing on your breathing before and during the interview can also help immensely.
Understand if there is a gap in knowledge or just getting ready to speak and perform in front of interviewer a challenge. Work on that gap accordingly.
We would love to talk about your challenges in detail and help a way out. Feel free to connect and sail through the interviews easily.