Relationship pickle... please help?

I have never done something like this before, but I could really use the advice.
My boyfriend and I have been together for over a year and a half, and it has been absolutely fantastic. We have been through so much together, and he is truly caring and loving.
Until recently.
For the last month, he has been very grumpy, said hurtful things, and has basically made me apologize and fix the hurtful situations that he causes.
Now, we have been in arguments before, and we work through them and they make us stronger. I know that we can last, and I know he truly loves me, but we can only last if he puts forth the effort. I love him with all of my heart, but I don’t want to be hurt by him just because he always wants to be right and make me fix these situations that he causes. My question is this: What can I do to make him realize that I don’t want to ever be without him, but I will not be treated so disrespectfully anymore?

P.S. I have already told him that we need to cool down and think about things, and that I will be here when he wants to talk. We both clarified that we are not breaking up or taking a break, just getting some time to think clearly.