It's great that your boyfriend is willing to get help. You have a working relationship. Now you need to know where to start. I am going to give you that gift.
First of all, both of you need to do individual therapy, as well as couples work. In your individual work, you need to focus on why you become self-attacking when your needs aren't being met. By doubting your needs, you are betraying the essence of who you are.
What you need (cuddling, affection) is part of who you are and what you need. You need to work on understanding why you don't feel entitled to stand your ground. I suspect that you were abused as a child, and made to feel that 'it'was all your fault. This would explain why you are so quick to turn the blame back on yourself, when, in fact, you are being neglected.
He needs to work on owning his angry feelings and talking about them rather than acting them out through withholding behavior. The way he withholds physical contact is a form of passive-aggression in which he releases his anger indirectly by refusing to give you what you want. He needs to learn the proper way to communicate his angry feelings in words not withholding behavior.
In couples therapy you both need to understand why this distance is occurring between you. You need to find out what you may be doing or saying that is making him so mad that he takes it out on you in this inappropriate way. You both need to examine what purpose this distance serves you as individuals and as a couple.
For example, if you felt mistreated or unloved as a kid, then his physical deprivation would make you feel comfortable. We humans tend to recreate what is familiar to us, and if you were used to feeling emotionally deprived as a kid, then your unconscious mind would arrange to recreate that situation in your adult relationships. Familiar pain is often more comfortable than the unknown.
For him, he may be comfortable with the physical distance because closeness scares him. Or, he may still be holding on to anger at his mother that he never resolved. Perhaps he is getting even with her by sticking it to you (or should I say not sticking it to you).
Both of you need to know that no pattern exists unless it meets the needs of both partners. I know that you consciously think that this pattern isn't meeting your needs. But, the unconscious part of your brain has a life of its own. And, as I said, if you were abused or neglected as a kid, then your unconscious mind will think that this is the way life is supposed to be.
In which case, your unconscious is quite comfortable with the pattern as it stands. Your conscious mind is balking, which is great. Now use your conscious mind to analyze what you are getting out of the situation, let him do the same, and you will be on the road to resolution.