You're confusing physical pleasure and pleasurable emotions with true happiness, which is the acquiring of the highest goods, which are known rationally. We know that the intellect is superior to the lower emotions and body since the intellect can choose to ignore or set aside various emotional and physical pleasures in various circumstances.
This passage from the Summa might be helpful:
I answer that, Since the ratio of good is the ratio of appetibility, as said before (5, 1), and since evil is opposed to good, it is impossible that any evil, as such, should be sought for by the appetite, either natural, or animal, or by the intellectual appetite which is the will. Nevertheless evil may be sought accidentally, so far as it accompanies a good, as appears in each of the appetites. For a natural agent intends not privation or corruption, but the form to which is annexed the privation of some other form, and the generation of one thing, which implies the corruption of another. Also when a lion kills a stag, his object is food, to obtain which the killing of the animal is only the means. Similarly the fornicator has merely pleasure for his object, and the deformity of sin is only an accompaniment. Now the evil that accompanies one good, is the privation of another good. Never therefore would evil be sought after, not even accidentally, unless the good that accompanies the evil were more desired than the good of which the evil is the privation. Now God wills no good more than He wills His own goodness; yet He wills one good more than another. Hence He in no way wills the evil of sin, which is the privation of right order towards the divine good. The evil of natural defect, or of punishment, He does will, by willing the good to which such evils are attached. Thus in willing justice He wills punishment; and in willing the preservation of the natural order, He wills some things to be naturally corrupted.We know objectively that the good for children is to be raised by their parents in a lifelong, exclusive relationship. This is intuitive, empirically demonstrable, and the norm for all of recorded human history.
The pleasurable aspect of intercourse, then, was orderd by nature to attain this end by serving to bring forth new life and to unite the couple. Anything opposed to this end is disordered and unnatural, and should be avoided, even if there are pleasurable aspects associated with it.
Translation: which are known because this is Aquinasfan's opinion.
We know that the intellect is superior to the lower emotions and body
Translation: we know this because this is Aquinasfan's opinion.
The pleasurable aspect of intercourse, then, was orderd by nature to attain this end by serving to bring forth new life and to unite the couple.
Translation: we know this because this is Aquinasfan's opinion.
Anything opposed to this end is disordered and unnatural, and should be avoided, even if there are pleasurable aspects associated with it.
Translation: we know this because this is Aquinasfan's opinion.
"You're confusing physical pleasure and pleasurable emotions with true happiness, which is the acquiring of the highest goods, which are known rationally."
Perhaps I am but that is my reality. I've traveled through life using emotions as a navigational tool. I seek out pleasure and pleasurable emotions and take failures and mistakes in stride. If I had to make a list of the things that make me happy, sex might make it into the top five (not sure, I'll have to think about that one). But wherever it ends up on the list, I don't consider sex wrong or that it's unnatural to do it just for the pleasure of it.
"The pleasurable aspect of intercourse, then, was orderd by nature to attain this end by serving to bring forth new life and to unite the couple. Anything opposed to this end is disordered and unnatural, and should be avoided, even if there are pleasurable aspects associated with it."
Birth control is unnatural but it certainly changes the nature of things. I don't think that's a bad thing. Oral sex and masturbation are opposed to the end you mention but I don't consider either activity unnatural. That's my reality. Different from yours obviously, but that's the way I think.