Fairly rapidly, your sperm part gets overtaken by practically all Steve's semen, and your consciousness in that part of you fades. But it feels weirdly tangential to the rest of you, more like picking dead skin from your feet than losing touch with part of what made you the person you were before all this.
Even so, when the new sperm reaches the ovum part of you, you feel weirdly... pliable. The satisfaction you feel instinctively overrides the fact that the person you're starting to become is clearly not the same one you used to be, as your xygote form settles in Mina's womb and impregnates her.
While you start to grow, you see the presentation being given in class about your re-birth, but you can't tell whether the teacher is worried and confused for you or if this was just a possible outcome of someone getting reverted to a sperm and egg and refertilized through sex.
In any case, the TVs started to show matter-of-factly what was happening to your genetics, and through the same quirk as your continued consciousness, you felt and saw it all in your mind's eye like it was happening to your regular body, even though right now you were an embryo. You saw the large letters XY, and the 'Y' gained another lower part to form a second 'X'. Not only had the new sperm that fertilized you come from Steve, it didn't even have masculine chromosomes.
The screen rendered your old body, and showed how it was reassigning its sex characteristics. Your shoulders narrowed and your arms, hands and upper body muscles slimmed, and a weird shiver ran through you as you felt your figure tighten up there. The screen moved down to your chest and your nipples enlarged, thickening and widening and feeling more sensitive, and soft flesh built on the previous flatness. Fantasies were quickly pervading your head, about having them licked and sucked and rubbed, and it started to dawn on you that more was happening than your body changing- you seemed to be changing mentally too.
Things shifted downwards, and you watched and felt as your previously straight figure slimmed and formed a noticeable curve, your skin softening all over with it. The narrowness your shoulders attained was counterbalanced by your hips widening as your butt and thighs rounded out, your legs and feet turning more lithe and small to fit.
Lastly came probably the most dramatic change. Your penis rapidly tugged inwards and your balls moved up inside you, your crotch flattening as your sexual fantasies started to feminize. Desires to have your body filled and fucked were quickly emerging, your shaft taking its new place as a sensitive nub to stimulate you rather than to fill others, and your scrotum sank into your body and opened inwards, the sac reshaping into lips and a space forming inside that felt almost as deep as your protrusion had been long.
Intense arousal was pushing you to a climax as the feelings of the changes sank in for you. This was impossible, and yet it'd happened- you'd been impregnated by a different sperm and turned into a girl.
You came to a few moments later, and looked up, seeing everyone in class stunned. You were in your fully developed body again, but you were the girl you'd seen yourself being turned into.