The setup seems flimsy, since there's no reasoning of why or how abundant sex works as a treatment for sudden magical core expansion. It just goes "You need to adjust to your magic -> ??? -> having sex helps you adjust to your magic, so for your own safety you have to have a lot of sex". I think Dumbledore would use more discreet terms than "having sex", and would give an academic explanation of the first and second steps, i.e. what happened to his magical core and what's involved in the process of adjusting his body to his magic, and let Harry draw his own conclusions. However, because if I'm honest with myself I didn't click on this story for a great plot experience, I can move past it. It would help, though.
One thing I cannot ignore, though, is the large number of semicolons where there should be commas or sometimes periods. You start off this chapter using commas, so I thought it might have been a one-time thing in the last chapter, but then I saw it again in this one. I hope it doesn't happen during a lemon scene.
Author's response
Hi, you aren't the only person to point out my excessive use of semi-colons, and, when I get the re-write done, I will be sending through a grammar beta process. And, I have to agree that the setup is fairly weak, but, it's something I plan to work on in the re-write. This story has actually been occupying my muse for the past week or so, and I'm planning, once I get my computer issues resolved, to actively start working on it.
Thanks for your interest
red