I have a 3-year-old son and am a first-time mom. I just noticed that he is very repetitive, saying something more times than expected. He doesn't stop, even when I say okay. He stops when he wants.
Is this behavior normal for a 3-year old?
This is a fairly common behavior in younger children (even somewhat older, my five year old does this).
"Mommy, Mommy, I found a bug!"
That's nice, dear.
"Mommy, Mommy, look, I found a bug!"
Okay, that's a nice bug.
"Mommy, Mommy, look at my bug!"
It's a combination of a few things. The child wants your attention, and wants it in a certain way. She also wants to communicate something to you; but she's not yet at the point that she can communicate it.
She's not just trying to tell you "Look, I found a bug"; she's trying to tell you that there is an interesting thing here that she wants to know more about, she wants to know if it's okay, she wants to know what to do with a bug.
She also wants validation and approval. She wants to know that what she's doing is a good thing, and that you think good things about her.
All that said, if you are still concerned about something, please ask your pediatrician; they will have more experience with your child than anyone here, and can tell you more confidently if there's any concern.