Just because you have BPD doesn't mean you're irrational for thinking 48 hours is too long without communication. Especially without any advance notice, that would upset / confuse anyone. You guys have a daily routine and he changed the routine without communicating it to you.

Don't self-harm or message him repeatedly, just simply let him know how you feel. "Hey <boyfriend>, we usually check in each day but I haven't heard from you in a couple of days, which makes me feel anxious. I know your phone is broken, but could you please try to send me a message each day just so I know you're okay?"

Then you are expressing your actual needs, rather than reacting out of anger. He can either meet that very simple request (in which case, great!) or he won't, in which case you can explore whether or not he's a good fit for you. That doesn't mean you're splitting or he's a villain, it just means there are plenty of people out there who are fine with communicating once a day with with their partner.