I don't know what to do from here, where am I going wrong

My fiance and I have been together for about 3 years and have a 16 month old son together.  He has always been a very caring and attentive person, but these last few months have been so difficult that I don't know what to do or if there even is a solution.  I feel like the life that I thought we had together is suddenly just falling apart or maybe I was just imaging that things were good before.

It seems like these last few months that the responsibilities and stress have just been to much for him.  If I try to speak to him about anything to do with bills, shopping, or household stuff he just seems to get so irritated.  No matter what the situation, if he gets irritated he becomes this totally different person.  Someone that is unable to be spoken to or reasoned with.  It's like he just shuts down, won't listen and doesn't think that he is doing wrong.  I am in no way perfect in this relationship, but when I make a mistake I admit it.  I don't understand how he can never except that he has done anything wrong.  He always manages to manipulate the sitatution so that I appear to be in the wrong.  When I know deep down inside I haven't done anything to instigate his actions.  When he gets like this (which is becoming more and more frequent) he doesn't listen, won't be rational and starts acting in ways that frighten me.

I keep trying to change the way that I approach him and not bother him about isssues unless I really have to.  I just feel like why should I put so much effort into changing myself if he can't even make the attempt to see his part in all of it.  What do I do?  Any feedback is appreciated!  I want to save our relationship, but I am getting to a point that I feel like I am always walking on eggshells, avoiding talking to him about daily stuff to avoid a fight and I am starting to feel like I am just a care taker.  As soon as I get home from work he goes and does his own thing.  I have to come home and make dinner, give our son a bath, clean, do dishes, etc.  I just feel like I am getting burnt out on trying and not getting anything back from him.