You’re sticking with psychological hedonism! This is a very controversial view, since it seems to make a lot of human behaviour very hard to interpret.
One might also wonder what reason there is for endorsing it – why suppose that we can’t act on any motive other than that of feeling good?
For more on this topic, you might read Chapter 5 of Rachels’ The Elements of Moral Philosophy. At Southampton, we run various modules that address these and similar issues: Ethics, Political Philosophy, Moral Philosophy, Happiness and Wellbeing, and Action, Reason, and Ethics. Many of our staff undertake research in this area, such as Dr. Alex Gregory, Prof. Chris Janaway, Dr. Sasha Mudd, and Dr. Jonathan Way.