I think your mother just does not know how to express how much she cares for you. In my experience, parents are often afraid when their children are going through hard times because they instinctively care for them. So if their child is emotionally distraught they try to block it out because it is painful for them too. Sometimes this makes going to your parents for emotional support a bad idea. This could be the case for you.

However, if you want to invest in a deeper connection with your mother it's not going to happen overnight. Communication is so vital and your anger is part of the problem I think. Please be gentle with her when you talk to her and ask her how she feels about your anger/whatever else you are telling her. This way you make it about her just as much as it is about you and she may become more open to talking about pain and brokenness because of it. In fact, you may find yourself learning things about her that you didn't know and you may end up having a better understanding of why she has been so unavailable to you.