How to break up with someone?

My boyfriend and I have been together a few months shy of two years. We briefly broke up for a couple of months and then tried to get back together. Since then, hes been really distant with me. Doesnt treat me the same, talk to me the same, goes several hours without responding, etc. Ive tried to talk to him, but I get nowhere and he shuts me down or blames me.

Tonight I think I reached a breaking point. I texted him when I woke up and never got a response. About 6 hours later I text him asking for a response. He texted me back that he was "feeling indifferent" about several things and was trying to get his mind right around them so he didn't "go off" on me. Im super confused at this point, we hadn't had any fights that i was aware of and I hadn't done anything wrong. I asked what was going on and then started to panic a little because it sounded like we were headed toward a break up.

He ignored me for several more hours and when he responded refused to talk to me about what he meant. Said he wasn't "in a position to discuss it" with me and was just really rude overall. He ignored me for several hours again. Now, I didn't blow up his phone with calls and texts because I'm also trying to process at this point. I reach out again after a few hours expressing my general concern and just wanting to know if hes okay because this attitude came from nowhere. At this point he wouldn't confirm or deny that his feelings of indifference were about me/us and my next thought went to his family because he said his mom hadn't felt well lately.

Still refuses to talk to me.

Now, this is not an isolated incident. He disappears all the time now. 0 affection, 0 kind words, 0 I love yous. I recently had a talk with him about how shutting me out increases my anxiety and then he does just that and puts the blame on me.

Overall, this relationship is not healthy. I want out, I need out. Im not happy and he obviously isn't either. We broke up for good reasons and never should have tried this again. But I don't know how. Ive never ended something like this before and we are long distance so I can't do this in person. Lately, I believe there may be another woman involved, but i have no proof where i cant be there. I just need some words of support, encouragement, advice..thank you ♡

Edit-

He continued to ignore me all night. I still haven't heard from him. Honestly, I'm hurt. I had all night to think about this relationship and I'm more sad about the fact I feel I wasted my time and have let someone disrespect me for so long. We broke up before because he is a narcissist, always using my anxiety or depression against me and then love bombing me afterwards. Sigh. Ive made up my mind that I'm going to end this today. There isn't any reason to stay in a relationship where I'm not happy, feel my needs aren't being met and feel disrespected.