I don't know too much on this situation because I am not one and was only with one person who I felt sort of was. Although she wasn't nearly as bad as this, but wouldn't take no for an answer, and I am talking about after I had to work 8 hours a day. So I know how you feel a bit but she could at least think about other things and talk about other things.

I am not sure that he is a sex addict and it's something he might think you enjoy? If not maybe it's just something he really enjoys talking about and doesn't realize that it upsets you. Addiction is something that can't be controlled right away so if you will completely voice your opinion to him and ask him why he acts this way then perhaps he will stop. If he doesn't then there probably IS something wrong and he needs to see a professional, and eventually you two will probably have to see one together.

Sorry if this isn't a lot of help but it's all I can offer, wishing you the best,