Actually, you are taxed and you do have multiple representatives in your local, state, and federal government. You may not like or support the legislation these reps enact, but you do have representation, nonetheless.
The British subjects in the American colonies, well, that was a different matter. "Taxation Without Representation" accurately described that dynamic. But not the ACA. Your gripe is with your elected representatives and your fellow citizens who voted in these reps.
Further, there's this underlying principal of laws for the common good such as schools, roads, emergency services, utilities, etc. You may not have children, for example, but the lion's share of your property taxes fund public education. You may not own a car, but a portion of your tax dollars fund the maintenance/construction of roads.
As for mandated healthcare insurance, you are only required to participate in the ACA if you do not have insurance provided or available to you via other sources. The uninsured have--in the past---used "free" medical services (such as hospital emergency care) for healthcare. While such service may be free to these uninsured individuals, that service is actually paid for by the insured parties. The ACA, in part, addresses this loophole.
America 101, revisited.