Some people have those kind of effects after smoking... Perhaps your father's blood pressure issues have a genetic effect on your inability to keep your heart rate down? Indicas would seem logical to relax you and lower your heart rate, but every body is different!

Try relaxing, deep breathing, and maybe some in-car meditation (while parked!) before you go into the house. It helps to calm your mind and body down very well. Avoid caffeinated, high salt, or high fat products around your smoke time. If you get the munchies particularly bad, heavy meals tend to bring the heart rate up, because more blood must be sent to your stomach and intestines to deal with such a large meal! It's good that you're smoking outside the house, especially if your parents have an issue with smoking!