I keep failing my boyfriend

I keep messing up unintentionally with my partner. He is a sensitive and kind person who understandably gets overwhelmed when I complain too much about something. We recently got into a big fight when I again, complained way too much about something that he found to be so minor.
I got upset too, although I did apologize. I ended up crying and in the midst of his frustration he laughed while saying something to me. I got even more upset and demanded an apology. He refused to say sorry, believing that since I started the whole issue he didn't see why he needed to apologize.
Feeling gas lit, I kept pushing for him to apologize until I lost my temper and cussed at him in a way I had never done so before. It was low and disgusting on my part and now he is distant from me.
He told me he had doubts about us and rightfully so as this is not the first time we have argued about my constant complaining.
I never intend to dump my complaints on him, they just turn out that way since I talk so much to him.
But I am aware that I have to take responsibility. And I did. I apologized profusely and agreed that I had gone too far.
I know I was in the wrong and I'm being held accountable for it.
I'm so afraid to lose him though.
How do I go about this? How do I fix things with him?