Your body just keeps changing

You obediently impale yourself on Cocephalos's massive shaft, drooling everywhere. Your mouth covering is already coated with slime as it rubs against the top of his cock as you **** yourself along it. Your legs burn as you throw yourself up and down, desperately trying to please your master. Your clit continues to drip and your ass waters, and again you find yourself leaking from all your holes. Cocephalos seems satisfied with your dedication, and as your legs reach the point of total exhaustion he commands you to freeze with his dick down your throat, then immediately begins to blast thick ropes of cum directly into your stomach. Halfway through he commands you to pull of his cock, and he blasts thick ropes all over your lewd body. Giants globs of cum run down your face and off your chest.

"Come with me," he says, begin to pull your chain as he walks towards a nearby tent.

You follow him as quickly as you can, your legs numb and wobbly. Inside the tent is a contraption you immediately recognize as the one the centaurs fucked you on before.

"For your sake I think this is our best option," he says, stripping your skimpy clothes off and then lifting you on and quickly binding your arms and legs to it, "Get ready for your reward."

He wastes no time getting behind you, bringing his cock to your tight little hole, then slamming in mercilessly.

As soon as he enters you, burying his shaft deep in your guts, you cum harder than you ever imagined. Your little clit feels almost nothing, but you feel an explosion inside your little pussy, and your entire body convulses wildly and clamps down on the invading member. He begins to brutally slamfuck you and you feel your anus tear slightly, but you don't care. As often as every second thrust he drives you to a wild, squealing, painful orgasm. You can't believe your own voice or behavior, but it doesn't matter. You're not in control, and you love it.

He uses you until you completely lose track of how many times you orgasm before depositing another load deep in your guts.

Afterward, he bring you down and to another tent. Here you see cushions and blankets arranged on the floor. He circles several times, then lies down, his legs splayed outwards and his huge cock exposed.

"Come down here my dear, it is time to sleep," he says, "But you still need a little training. Slide your little pussy onto me while we sleep, it will help you learn how to fulfill your duty."

You obey before you even have a chance to process his words, laying down beside his equine chest, then sliding your ass onto his cock. You push it in as far as you can go, then lie down and try to sleep.

Life continues like this for you for several weeks, though you have no idea where you're going or how long it will take to get there. You haven't eaten any real food, and you drink little water. Instead, your main sustenance is the strange but pleasant liquid they continue to feed you, as well as Cocephalos's cum and sometimes his piss. As you travel, you notice changes to your body.

You have begun to grow breasts. After two weeks your chest has expanded to the point where you have breasts most women would be more than happy with. Cocephalos notes their growth every day with great joy, sometimes holding onto you just so he can **** your chest. Even more concerning, however, is what you feel deep inside you. Something isn't right. It's as if there is some presence, perhaps some cum that you couldn't get rid of, and it is steadily growing. After a month of travel, Cocephalos stops the daily routine of fucking you and seems to mostly leave you alone. By this time, your abdomen has begun to swell quite visibly. You are terrified, not knowing what is happening to you. You don't know if it is a disease, or if it is some sort of parasite or growth or curse. You also begin to experience random bouts of nausea, which at first you cannot explain. A sick understanding dawns on you, however, when you see Cocephalos disgustingly ogling your swollen body. Far from concerned, he seems thrilled and aroused. The pieces fall into place as you remember all the specific words you had heard them use before.

You thought you had experienced the ultimate emasculation when they took your balls, but you realize now how wrong you were.