[Meizicht]

Well, if it were me, and the situation was me and my boyfriend with the information you've given, the source of my anger would be more... "He didn't listen to me"/"I'm tired of being a stupid shit"/"Instead of thinking too much on it, I'll spare everyone by making him hate me".
I isolate often, but I simply disappear off the face of the earth instead of getting angry with people. So I'm not exactly sure what must've happened. I know there's probably a lot more to it, so it could be many things.
Wish I could tell you more; all I can tell you is my own behavior which seems similar.
All I can really say is if this isn't pity of any kind, and you really do love him, don't message him a lot; just give him a long, honest message about what you genuinely think. Like what you like about him, how much you miss him; if something happened to cause his shutting out, maybe explain your side ( if it has to do with you, Iknownothing,so ). But if you're not sure in any way about loving him, if you have any doubts, then the best thing would be leaving him be.
I speak from experience; it doesn't matter if we don't feel much, I know I get attached so badly that if the other person isn't in 100%, it'll break me beyond repair. I had a relationship like that a couple years ago, and I wish he would've simply broke it off with me quickly instead of letting it ride out. x__x;
I still haven't really recovered and I unintentionally make Kai ( my boyfriend ) suffer from it. Since I'm a huge glacier, affection-wise. OTL ( I used to practically shower my ex in affection, but then it ended very badly. I can't really bring myself to do all that now, lol )
Saying all of this in hopes that my experiences might give you some kind of insight. Again, I don't know him, so I can't really say anything for sure, lol.

Either way, whichever the outcome, I hope you both work it out. If you're together or going separate ways, only thing that matters here is if people are happy or will be.