I Can’t Stop Being Mean (help)

Hi there. I could use a little help. I tend to ramble so I’ll try not to do that here and be more precise. 
4 and a half year relationship with a really amazing man. We’ve been really up and down in our past and we were both unwell and untreated.
Recently we’ve decided to just try and give this relationship a go since we have both put in a considerable amount of work to be better and it’s evident in both of us. 

However. It’s long distance this time. 1,200 miles  away to be exact. Visiting has been hard now due to all the COVID issues but before that it was financial situations blah blah blah. We literally worked out a lot before this whole thing happened. Anyways both our states are loosening up travel so we’ve been trying to make responsible and viable plans to start seeing each other more often. Great. Cool. He just visited for 5 days last week. It was heaven. Now...we’ll I’ve been out of therapy because my services shut down and didn’t call me for 3 months nearly to do phone services despite me leaving multiple, scathing voicemails. So I’ve been kinda like a little not well. But still a little better. 

Anywho. My point is. My boyfriend is fantastic. He does so much for me. Literally such an angel, so kind. He listens and compromises and is my rock all the time. Yet lately...I can’t help but fall back into old ways. I’ve been snappy, course, unwilling to be flexible. Very just mean. So mean. And it’s hard because one I’ve been doing so much better and two, sometimes I don’t even realize it until it’s too late. Then I just feel like shit and beat myself up for days which leads to me tending to shit down. I really do love this man. We have been through so much together and we are finally getting a chance to build the life we want but I think I’m getting cold feet, and not due to any kind of not wanting to be with him but after dragging my feet for so long and trying to undo all the past issues I’ve had that make me act the way I do according to diagnosis. Lately I’m just backsliding and I’m trying but I’m not doing as well as I want. Please help. I don’t want to be mean to him anymore. 
I try to breathe and am generally good at communicating/asking for breaks/empathizing. The whole 9. But lately it’s so hard. I can tell myself not to go off but then as soon as I open my mouth it just spews out. 

Also; I’m 23 now and was diagnosed at 19 with suspicions developed much sooner. I’ve been in domestic violence classes, therapy, medication. I’m very fortunate to have found support as soon as I did. However I still struggle