Maybe it is that you enjoyed doing work on A, and you were consumed with the control and enjoyed him. Now that he is gone the control is gone? Man B is not needing that control and the sexual energy is not there. Usually with some people sex is also a part of control, controlling someone is power, power is related to sex, in the most innate way. Some may disagree but when you think about humanity, and how we mate...usually those with power get the best to breed with.
I know this problem very well myself. In an abusive relationship there were power struggles and the sexual chemistry was intense. Now with a man that is sincere, loving and would do anything for me the chemistry is labile, coming and going. I have been trying to free myself from this and I have abstained from sex for awhile and tried meditation and control within other areas of my life. I think it is helping.
If what I said above relates to you then breaking-up with your past actions is what you are doing, seems guy B is better for you and you realize that, so that first step is there, also noted is that you are reaching out asking for help.
Anger can only go away by forgiveness. Maybe making peace with the past of guy A can help with the future with guy B. I am in process of the whole making peace with my past and it is not easy. People in my life that were in my past have died, I have had to head on go back to my past and make peace with it, whereas I have ran from before. So with that I can only say to bring love, peace and happiness into your life by knowing you deserve it.
