I think you're basically right about how the discussion goes on this point, but it's not necessarily a "fallacy."
First off, a minor correction in structure:
since the action is obviously good, it makes you happy, and that is the consequence that matters.
I think the consequentialist position is that the reason an action is "obviously good" is that it makes you and/or many happy. And that this is why we can even call it obviously good. (i.e. obviously good follows from rather than causes making happy on this picture).
Second, I'm going to use "consequentialist" here to refer to the sort of utilitarian version of consequentialism you use in your question. There are many others that would gum things up and not work for your question.
Third, let's look at what you're saying vs. what they're saying.
C's Argument (at its most basic and simplified):
- Any action is good because it makes you happy
- Action q makes you happy.
- Ergo Action q is good.
This picture is accepted by consequentialists (broadly speaking and varying by consequence of interest). But it's rejected by Kant and Aristotle.
For Kant, it's something like this:
- Any action is good to the extent that its maxim is universalizable and respects humanity (rationality).
- Action q is undertaken under condition 1.
- Action q is good.
- Action q may also make you happy.
and/or some good actions don't make you happy (for Kant, this is one reason why we have to be immortal and there must be a heaven and hell to even this out) and some people experience happiness at evil.
- Any action is good if the phronemos (man of practical wisdom) would choose to do it under all the same circumstances.
- Any good action brings pleasure to the phronemos in expressing excellence.
- Action q is undertaken by phronemos.
- Action q is good and action q brings the phronemos happiness...
- Action q is undertaken by Joe Schmoe
- Joe Schmoe is not guaranteed to experience happiness.
- Action z (some obviously wrong action) is undertaken by Joe Schmoe.
- Joe Schmoe might experience happiness.
In a sense, given this picture, we could say is that consequentialists are question-begging when they assert that actions are good when they promote happiness. But I'm not entirely convinced they are doing something fallacious. I take it what they believe they are doing is observing empirical phenomenon and identifying the word "good" with the empirical phenomenon of pleasure-giving. Thus any time they see pleasure giving, they say "good."
People with other views are not convinced because they don't share an empiricist assumption about morality held by the consequentialists. I think for the consequentialist to engage in a fallacy, what has to happen is that they don't acknowledge they are making a metaphysical claim that undergirds how they are interpreting empirical data. Some consequentialists do this; others don't.
Bernard Williams has an interesting article on this point highlighting that consequentialist theories often seem to be post-hoc explanations of right and wrong which are always checked against something else. In other words, most utilitarians want murder to be wrong, so they try a quantitative theory and test it against things they already consider wrong.