This is a very interesting question, and I think there could be lots of explanations. The first thing that comes to mind is that maybe you experienced more abuse in childhood than you realize. I have worked with many clients who remembered early abusive experiences much later in life, sometimes after something triggered the memory. Sex is obviously a very intimate act and you may feel vulnerable, even when you are with someone you trust. These feelings may be a gateway to other deep feelings. Perhaps the verbal abuse you do recall damaged you more than you realize.
Self-harm can mean many things also. It can be a way of coping with emotional pain, a method of grounding yourself to the here and now, or inversely, a way of dissociating. Ultimately though, it is self-abuse and you can find many other healthier ways of coping.
Finally, there are many who state that sadomasochistic sexual tendencies are perfectly healthy, however, I have trouble accepting this notion. I would suggest that you consider exploring these issues at a deeper level with a therapist before they get worse or you develop fear or resistance to intimacy.
All the best,
Dr. Holly Counts