Well technically the heart isn’t formed enough in an embryo to beat until it’s around 22–28 days old (or 5+ weeks gestational age), but that doesn’t really matter for your argument. You know what an embryo doesn’t have at that age? A brain. Or a central nervous system. If you can reduce being human to any one single characteristic, it’s the ability to experience. And embryos don’t have the ‘hardware’ in place to experience anything until the third trimester.
(PS — fingers and toes don’t develop until about 7 weeks post-conception / 9 weeks gestation)
There’s nothing wrong with hating abortion. But if you really want to reduce unwanted pregnancy and by extension, abortions, slut-shaming (or lazy-shaming?) isn’t the way to go. Instead, I would hope you support fact/evidence-based sex education along with ready access to free/affordable healthcare.