Dear Perfect,
distant and irritable means there's something that bugging him. First off, you need to have a talk with him when the two of you are alone. Find out wuts up with that attitude of his and discuss your relationship together calmly and maturely. If you are serious about breaking up with him...or have contemplated it but you are unsure...then you need to explain to him that this is serious and we need to talk about it right now. Do this when you two sit down to talk.
Now if he's unwilling to do this...for some reason...which he won't explain...then you can break up with him if you choose to. But you must absolutely make sure that you tell him that this discussion is serious and there's no time for games.
Never jump to conclusions...cause you don't know exactly what it is. The only way to find out is to talk with him...all we can do in situations like this is advise you based on the information you give us. Our advice may not necessarily be correct and accurate because we don't know the whole story. However, you do...and my advice to you is to sit down with him...and have a serious discussion about wuts going on with him.
I hope things clear up
-Beachead