If it is any consolation, what you are feeling is pretty normal. Even with a planned pregnancy, many women have torn feelings because it is such a big life change. It can be a little more difficult with an unplanned preganncy because you had other plans and this is throwing a big wrench in them, and some people don't like when things mess with their plans. It's normal and ok to be happy and sad at the same time. Try to talk to your husband- he may be more helpful than you think, and may also be having similar feelings but is too afraid to share them because he thinks that all you want to see is happy. Consider talking to a counselor to help you get to a place where you are more happy than sad.
I'm not sure what adventures you think you can't go on now that you will have a child. They may have to wait, you may have to find a sitter or alter them a bit to make them a better fit with a small child, but you are far from being stuck to your home for the rest of your life. They are only babies for a short while.