you are harry james potter, and the dursleys have always known you were a freak. you were a freak because you were dark skinned, you were a freak because you were not real, and they told you this time and time again. they called you "boy" while the doctors told you you weren't a real boy, because they wanted you confused and in the dark. they made you make the flower beds and get hit by frying pans and they ignored you for ten years of your life. all because you are a freak.
in your second year at hogwarts, you discover the reason for the doctor visits. you start bleeding, and madam pomfrey tells you you have what the muggles call progestin-induced virilisation. you don't care what it's called. you hate it, hate the implication it has that lily potter, the mother who sacrificed herself for you, did drugs because she didn't trust her own body enough to not lose you, and you hate yourself for being this kind of freak, the kind even the wizarding world can't fix. you don't tell ron. you hide the pads, and the one time seamus finds them you tell him you were borrowing hermione's backpack for something. he still looks at you funny, and it brings you back to primary school, lying in your cupboard because dudley scared off your new friend, and he looked at you with that same glare. you deserve the glares though. you deserve what you get.
the dursley's neglect begins to sting worse the older you get. your puberty begins masculizing you, but you still aren't fed enough and you still have to dodge soapy frying pans and stay locked in your bedroom when you mouth off. you still get fed, when you do, by the fucking cat-flap on your door. you know ron doesn't live like this, you've been to the burrow, and so it hurts all the more.
when umbridge accuses you of being a liar, you are angry, but not surprised. you have been called a liar, an attention seeker, a manipulative, dangerous freak, for as long as you can remember. when umbridge gives you the blood quill in detention, you are surprised, but you keep it a secret, for the most part. when umbridge pins you to the floor after you stop writing lines when she wants you to continue, you are shocked. when she rips your robes off and touches you, calling you a freak, a dangerous creature, a liar for pretending to be a boy, you are frozen. and when she rapes you, you are silent. you must not tell lies, after all, and if you getting locked in the cupboard in year four was a lie, certainly getting raped by a woman is one. you must not tell lies. you are to blame for being such a freak anyway. you deserve what you get.
when snape penetrates your mind, he doesn't know how good at occlumency you really are. he sees the dreams of voldemort, sure, but he doesn't see umbridge. he doesn't see the years of being told your existence is a burden, the years of being ignored or criticized by your aunt and uncle. he doesn't see how your childhood eerily mimicks his own, only you were not the victim of only your family. you have trauma from the incident that you never talk about. he sees none of that, because your brain is naturally better at occlumency than you can tell. and so he continues hating you for looking like your father, instead of noticing how often you can't look adults in the eyes.