No, a fetus does not have a heartbeat at week four of conception. That's not science. Feel free to put a stehoscope to the belly of a woman six weeks pregnant and listen for a fetal heartbeat: you will hear none. At about six weeks, there is some electrical activitiy that our more sophisticated unltrasound technology can detect, but that is also not a heartbeat, because the organs haven't formed yet, so there is no heart. It's hard to have a heartbeat without a heart, just like it's hard to have thoughts without a brain. The earliest that an organ forms that looks remotely like a heart is somewhere between ten and twelve weeks, and even at that point it isn't viable without significant further development. We regularly declare adults legally dead when their hearts are working just fine if they lack higher brain functions, so that's the standard we regularly use to judge life in adults. A fetus doesn't have the capacity to demonstrate the coordinated brain activity required for consciousness until at least week 24. Saying a fetus has a heartbeat at four weeks is a science-free emotional claim akin to saying that if I take a piece of roast beef out of the fridge and hook it up to a nine volt battery so that an electrical charge runs through it it means that it's alive and somehow has more rights than a grown adult woman does.
More importantly, you are very clearly missing the most important distinction here, which is that it's not "my body, my choice" when the choice you want to make with your body directly endangers the lives of other adult bodies around you. A woman who feels she is incapable of being a good parent, and is the person who is in the best position to know whether or not that is the case, does not risk killing dozens of strangers in her community by having an abortion. An antivaxxer unmasked can kill a bunch of adult strangers by spreading a disease which has already killed more than four million people despite the largest collective effort to contain an infection in the entirety of human history. That wilful endangerment is not "my body, my choice" but "my body and the bodies of everyone else I come in contact with, my choice and expressly against their will." That's why all of the people with PhDs in epidemiology including the ones who successfully obliterated smallpox are in agreement about the public health danger antivaxxers create. When the thing you want to make a choice about involves only what happens inside your own body, that's your choice, and when the thing you want to make a choice about takes away the choices other people have about their bodies, you don't have that right.
It's "my car, my choice" if you want and can afford to own a car, and you get to choose to drive it to the bank or across town to visit your sister or to a completely different town. It's not "my car, my choice" if you want to drive drunk at double the speed limit in the wrong lane just because you feel like it, because that needlessly endangers the lives of everyone on the road. It's "my gun my choice" if you own a gun and take it to a shooting range or buy a permit for a hunting trip, but it ceases to be "my gun my choice" when you want to start shooting it blindfolded in a crowd.
The hypocrisy is someone saying that reminding antivaxxers that they are endangering others around them is wildly unacceptable, but then saying that a woman shouldn't even be permitted to end a pregnancy that endangers her own well being. That's hypocrisy. If I say that a woman shouldn't be forced into an involuntary commitment that will reshape her entire life for decades, it is because I value her independent quality of life, and if I say that an asshole shouldn't be welcome to infect her with a disease that might kill her, it is also because I value her independent quality of life. There is no contradiction. There is instead this thing we call compassion, or human decency.
Stop pretending that the equivalent of "making me drive only on the right side of the road just because it protects people's lives is tyranny, and I should be allowed to drive on whatever the hell side of the road I feel like" is somehow a personal choice that can impact only you personally. It's intellectually indefensible and morally reprehensible at the same time. Be better than that. You might like it if you tried it.