when I try to talk to him about our sex problems and our relatonship problems he either doesn't want to talk about it or he says it is my fault
I don't see this as a problem only about sex. As you said in your question, it is also about the relationship problems too.
The problem with having either of these, or both of these problems, is that he is not admitting to what the cause is.
Is he interested in someone else, has he just grown apart from you, does he feel that the two of you are incompatible and he's questioning the future?
The relationship problems include the lack of sex; the lack of sex is part of a bigger problem.
If your boyfriend will go to couples counselling, or make a sincere effort to address your concerns and not ignore them, then trying is certainly worthwhile. Without him doing at least that, you have nothing left to work on. If he refuses to communicate, and the two of you keep spinning your wheels, the relationship will crash.