No. In Jamaica, the land your house is on is not directly owned by the British monarchy. While Jamaica is a constitutional monarchy with the British monarch as the ceremonial head of state, land ownership in Jamaica operates through its own legal framework.
Most land in Jamaica is privately owned, and land ownership is regulated under Jamaican law, which includes titles registered through the National Land Agency (NLA). The Crown, as it relates to land, does own some properties—referred to as Crown land—but these are usually specific public lands set aside for government use, conservation, or other purposes.
If your house sits on private land, it is owned by either you, a private individual, or a private entity. Ownership would be confirmed through a registered title. To clarify the status of your property, you can check your title with the NLA, which keeps records of land ownership throughout Jamaica.
In short, while Jamaica recognizes the British monarch as the head of state, the land ownership laws are governed independently by Jamaica. Your property is not owned by the monarchy unless it is registered as Crown land, which is rare for private residential properties.