Do you have a therapist? If you do, s/he may be able to help your family understand what you're going through and how to help you.

If not, can you try writing it down for them? What you said here was really clear and coherent, and I think it would make sense to them, too. It really comes across that you want to make things better and are doing your best, even though it doesn't always work perfectly.

Long term, it sounds like working on your triggers might help. Do you know what triggered you last night? Once you can identify the trigger and understand where it comes from, that often makes it a lot easier to slow down between when the trigger happens and when you react. It helps me to be able to say to myself, "Look, it's not as bad as I'm feeling. I'm reacting to this situation strongly because it reminds me of XYZ from my past, but that's not happening now. What's happening now is ABC, and I don't have to react to it the way I did in the past." It's not perfect, and I still sometimes react to a trigger before I can understand what's happening or stop it. But it does get easier the more you work on it.