I need an internal heater that works

Someone needs to explain something to me. Or they need to figure out why I'm so weird. Here's the situation. During the Winter, in an attempt to keep our bills down we tried to keep our heat at around 65. Which might not be cold for you people up North, but for me it was pretty reasonable, although I turned it up any chance I got. Anyway, our bills lowered and all was well in the world. Then it started to warm up. The sun would come out and I would open my blinds and again, all was happy in the world. I even turned the heat off. Here's where it starts getting weird. I turned the heat off and I was fine (as long as the sun was shining through my widows) even in the temperature in my house was at 61ish. Whatever, I was saving loads of money right? Well, here we are well into Spring and the heat is off for good (unless it's a really cold rainy day). Temperatures are high sixties, maybe even 70's outside, and it is just beautiful and lovely. I couldn't ask for more....expect I'm freezing! My house right now is 69 degrees, and I'm wrapped up in sweats, sweatshirt, and three blankets. Yet a month ago I was okay with 61 degrees. Hello, something is wrong with this picture. And I'm guessing when it gets really hot here 69 degrees will just be too hot. What is a person to do?