I am a graduate engineering student at a highly competitive university. I am writing my thesis and I feel like I am making great number of silly mistakes. The worst thing is that I do not realize my mistakes unless someone else points out even though I spend hours trying to make sure I make no mistakes... For instance, I modeled a problem in my thesis. I made a mistake that is very obvious and I didn't even notice that simple mistake until someone pointed out. I am about to submit my thesis and I have no clue how to tell my supervisors about the mistake...
I feel really embarrassed before my supervisors. They have been acting nice as they know I am a very hardworking student. Around 4-5 months ago, they even told me that they would recommend me to any university in the world. But I am afraid that they may feel less enthusiastic when writing reference letters for me (coupled with observing some personal decisions of mine, I am the exact opposite of a person who has their feet on the ground, I always have very big goals and dreams) because of my consistent errors and because I disappointed them. I feel extremely dumb and have started to feel like I have dyslexia or a similar situation.
How should I tell my supervisors about this latest error? How do I cope with this?