The area of sexual addiction is very broad and several papers and dissertations are available on this topic.
There are few general themes you may want to consider:
1) Sexual addiction and its effects on an individual (social, personal, professional, health, etc.)
2) Causes of sexual addiction
3) Perception of sexual addiction
4) Treatment of sexual addiction, etc.
Some of the general thesis statements could be (and these do not include the run-of-the-mill topics):
1) Does sexual addiction lead to rapes?
2) Does internet pornography and its easy access exacerbate sexual addiction?
3) Are sex addicts sexual offenders?
4) Differences between homosexual and heterosexual sexual addicts.
There is a great article on enotes about sexual addiction, along with an example report. You may want to go through it for more ideas.