Thing is, OP - what do you want to do? You're just going round in circles and brooding on it all time and time again.
By your own admission, if you finish this relationship you'll never have another one again. This sounds like a close, loving set-up with the group and with your boyfriend. That's a huge loss to just chuck away.
Do you think you'll be leading your most fulfilling, best life to give up on other humans and hide from relationships because you can't stop talking negatively to yourself?
If people choose to be single because that's what makes them happy and fulfilled, that's one thing - but in your case, you'll just be hiding from feelings which are too complicated and scary for you to confront. That's something very different, and would be very sad. A half life.
You've continued to use the same kind of negative language throughout your posts here. So despite saying you've had therapy and are using the tools - you're clearly not.
I have any own story, and my own trauma, and my own horrible anxiety. I know how hard it is to deal with feelings of inadequacy. But you're not even trying. You've had a very grownup conversation with him, and he's given you all the reassurance you could possibly need. It's now up to you to decide to proactively refuse to entertain those thoughts. You're allowing yourself to dwell on them and using very negative language.
Being in a relationship isn't a competition with other women. Your boyfriend wasn't comparing you - he was clumsily trying to lift you both up.
And just for reference - the woman who you have described as cool, pretty and the person everyone wants to be with, her OWN HUSBAND told her that he'd marry you. I mean, jesus. Your boyfriend saying that you both looked pretty pales into insignificance alongside that. So if you need any proof that you're as worthy as her - there you go.
You're in the middle of a black hole at the moment and if you end things now, when you finally climb back out again, you could well regret acting on these feelings of low self esteem.
When I'm at my worth, I struggle with feeling to deserve feeling happy - I had to fight very, very hard to accept people showing me love because I feel as if I'm such a horrible person, that I don't deserve it. So I engage in self sabotaging behaviour because I feel that I don't deserve anything more. There's an awful kind of satisfaction in making yourself feel bad because it feels that's what you deserve.
Whatever the trigger, whatever the cause - it's never helpful to listen to that destructive inner voice. You know this. If you keep talking over the loud and persistent inner voice that wants to drag you down, eventually it gets quieter. But you have to want to try - it's not going to melt away on its own.
Up to you OP. Your call. Your life. We only get one shot at this - would be a shame to throw away genuine happiness over something which will eventually fade and pass. But it's your choice.