We split due to arguments. Mainly bought on by lockdown and both being stuck home and off work together. We rarely argued however, when we did, it would be really upsetting & i would obviously call my friends crying, we would have some space, figure it out over a few days and then be ok again. But the last one just went too far,
OP, I know nothing about your relationship but the above few sentences throw up so many red flags for me I'm not surprised how your friend feels, particularly if she's the one that you routinely go to when things are bad.
You claim arguments were caused by lockdown - except that you've broken up 4 times in 6 years so there's ALWAYS something. And clearly you're in denial. She probably sees this very clearly.
When you argue, you call your friend crying - most people do not do this. Many of us do talk to/rant to friends and family when we've had an argument etc, but the only time I can ever remember calling a friend crying was when I really believed the relationship was over. In that instance, I was scooped up and given love and assurance. Your friend, seeing this level of extreme responses over and over again, is probably not only tired of it, but unclear why you'd stay with this man.
"But the last one just went too far" - what does this mean? After what is clearly a number of arguments that were so bad you were calling your friend and crying etc etc, finally it went "too far". I'm guessing too far is something like violence or the kind of verbal abuse that's just impossible to return from. Again, I'm guessing your friend finds it incomprehensible how you'd go back to this.
And you both have kids in this too?