I think we might have to agree to disagree on that one!
Yes, we do get messages from the reward chemicals in the brain. We get those when we have new relationships, or when we exercise, or when we have orgasms. I don't think we necessarily are "addicted" to that feeling, we just like it. I think that people often use the term "addiction" to refer to things we really really really love and want to do because they feel good. As in "I'm addicted to exercise." But it can get overused in a therapeutic sense.
Of course, feel free to disagree. This is currently an issue among Sex Therapists, the community isn't in agreement, although the majority seem to be eschewing the diagnosis of sex addiction. I think many therapists are just getting way too many people using the term "addiction" because then it becomes a medical problem that needs to be fixed, instead of a relational problem that needs to be delved into, discussed, and worked on between BOTH partners.
I do think that people USE sex, and food, and alcohol and all kinds of things in order to feel "good" and cover up other issues that are too hard to face, that they are unsure of, that they aren't ready yet to deal with. Personally speaking, I suffer from anxiety, and my mind can race out of control to the point where I literally cannot stop the thoughts from happening. I would often drink because after a glass or two of wine my brain finally stopped. I was not addicted to alcohol, I was using it to self-soothe my anxiety. Going to AA and ditching alcohol isn't going to solve my problem, I have to delve into and work on the underlying problem, the anxiety.
I also don't think using the word "addiction" to apply to things that are necessary for a healthy life. When people overdo something like food, sex, exercise (parts of a healthy life) to cover up other issues, it's not the food sex or exercise that's the problem. It's the issue underneath they're trying to cover up. That's why I really prefer the term "out of control behavior" as opposed to addiction. If I am exercising 6 hours a day because I have body dysmorphia, then I'm not addicted to exercise, but I am out of control with my behavior.
Anyway, that's my 1-1/2 cents worth... :-)