Criticisms are healthy in a relationship; you challenge each other to be a better person. Without knowing what criticisms he has of you, and what criticisms you have of him, I can only say that such criticism should be constructive, something that both of you can take on in good stride and be able to consider change. Not many can tolerate criticism delivered in a demeaning manner.
An example I can think of, which is very superficial but I'm sure is very common, is becoming fatter. The best way I can think of to convey that your partner is getting fat, is to suggest going to healthier places to eat, and joining a gym with them. I have done this with my partner - actually, it's my partner that made the suggestions LOL - and because of the way the criticism was conveyed, no feelings were hurt. I'm not much fitter than we first started going to the gym and eating more healthily, but I can say it's good to know what my partner is thinking and that I'm on the way to a happier relationship with her.
At the end of the day, sit down and talk honestly with him. Tell him you do not appreciate blunt criticism, and to consider what he says before he says it. Tell him if he loves you, then he should consider your feelings. Tell him you're willing to take on his criticism only if it's constructive and that he can help you out with them. And the same applies to you. Make sure your criticisms for him are reasonable and something that he can work on with your help. I understand there are people out there that are just not receptive to any criticism, and if your guy is one of them, then I'm sorry, there's nothing much to do.
"Tell him you're willing to take on his criticism only if it's constructive and that he can help you out with them". Cringe :) They are wayyyyyyyyyyy past that point. This post is not a first attempt but a last attempt at saving a doomed relationship. Stay strong girl!