Generally it can either be ones feelings about oneself or ones past experiences, usually the two link in some way
A misconception commonly used when violence occurs in a dating relationship is that "he/she only hits me because he/she loves me". This however is not true. In a relationship, one will not abuse their partner out of love. it is not affectionate. it is purely out of rage, anger, low self-esteem, or upsetting circumstances.
Alcholicism kills brain cells and two suggestics would be to go to a rehab or speak to a therapist
It really depends on their age. You also cant just assume all patients are on birth control.