Nobody's insulted you except your b/f OP.
And please think about working on your self-esteem. You're not alone in having confidence issues, there's no "kicking" implied when PP advise you to work on that, & your boundaries, & the bar you set for how this man treats you.
But when you say the worst of it was that your b/f humiliated you in front of your friend & you are more concerned about feeling embarrassed in front of a 3rd party than you are horrified that someone who is meant to love you has been a massive bellend to you, PP are going to be concerned.
Why is the fact that your friend overheard, more important to you than the fact your b/f insults & denigrates you?
You friend's opinion isn't more important than yours, is it?
So why is it ok for your b/f to insult you (as you are now brushing this under the carpet & clearly intend to do nothing about it) - but not ok for your friend to hear it too?
Is being in a relationship so compelling to you that you will put up with this awful behaviour rather than be single?
Does it not matter how poorly he speaks to you, so long as nobody else hears him doing it?
Why are you according yourself less respect than you accord your friend?
Of course your b/f has good qualities too.
A delicious sandwich with your favourite fillings has good qualities. But if I served you your favourite sandwich, with just 5% shit in it, would you eat it?
So why are you tolerating this 5% shit in your relationship?
What are you going to do about this now - have you even spoken to your b/f about how unacceptably he's behaving?
& again - NOBODY HERE IS KICKING YOU. PP are simply concerned that your b/f is showing you the thin end of a very ugly wedge.
Here's some weekend reading for you that you might find very helpful - www.amazon.co.uk/Woman-Your-Own-Right-Assertiveness/dp/0704334208?tag=mumsnetforu03-21