Need AC unit for second story

In the past week I’ve made a huge life change, bigger than anything I’ve ever done before. I relocated myself, my guinea pig, and all my belongings 700 miles south of where I had lived for the past 6 years. It’s also 1000 miles from my hometown, and I’ve never been so distant from my family before. I have to say, I don’t think that this big change has really set in yet since we’ve been so busy running around and getting the new place set up, but the shiny newness of the whole situation is definitely wearing off already, especially when I think about the new house’s central heating and cooling system. I love the new place we are residing in; it’s a big house with a wooded yard and a ton of room for our dog to place. However, the house has difficulty keeping a consistent centralized temperature. There are several floors, and each one is distinctly heated from the last. I first noticed this quality when I tried to sleep on the first night here, and realized that the top floor was much hotter than the thermostat readout. I lowered the temperature significantly and received a lot of flack from my boyfriend for overusing the central cooling, but couldn’t sleep unless the AC was adjusted this significantly. Since then, it has continued to be a topic of conversation, and I think we may have to buy a window air conditioner unit to reduce the interpersonal contention spawned by this indoor air temperature discrepancy. Then we can both sleep at night.