It's about as close to impossible as you can get. If you tried to do it in the womb, too much deviation from a regular human fetus won't be carried to term. If you try to do it after growth plates have closed, you'd have to destroy every bone in the body first, which would kill you. That gives you some kind of post-birth, pre-puberty window over which some sufficient level of body remodeling can at least happen in principle, but you seem to be underestimating the level of remodeling to do this. You'd need to drastically reduce bone density, which would leave you extremely susceptible to injury. You'd have to undo human adaptations in the spine and pelvis for upright posture, which would be extremely painful. You'd need to effectively swap out the glutes with pecs and undo the adaptations for brachiating arms. Things like your eyes and ears and basic breathing apparatus are not well-adapted for flight. Things like where blood and lymph and other bodily fluids tend to pool in the human body versus where they do in the bodies of flying animals. Just as laying down for too much time will cause it to pool in places your body can't easily clear right now, being horizontal for flight would have the same effect.
It's not just a matter of growing wings. And yeah, the energy demands of making all these changes, as others have pointed out. The only kinds of animals that go through this level of non-fetal metamorphosis are insects with weights measured in the tens of grams, energy needs that kind be sustained by something like a cocoon. How would you meet the energy demands of an adult human going through metamorphosis? You couldn't do it by eating, not only because your gut can't actually digest the amount of food you'd need (you don't have an elephant gut) but also simply because being conscious through the process, unlike insects in a cocoon, would be so absurdly painful that I doubt you'd be able to function and do anything at all, let alone spend all of your time finding and eating food. You'd need to be put into a medical coma and injected with intravenous nutrients to have any shot at all.
Why on earth would we ever try this? In reality, giving yourself genes to grow wings would just kill you.
Look at this picture from Wikipedia showing Argentavis side by side with a human: https://en.wikipedia.org/wiki/Argentavis#/media/File:62628-A...
What sorts of processes do you imagine are necessary to stretch the human body to the size of the Argentavis body without adding any weight? It'd be like getting flattened by a steam roller, then drawn and quartered. Bodily tissue isn't balloons.
