If something is seriously wrong, then knowing what it is will give you and your doctor the best chance to fix it. And if it's something simple, all the better. You're under stress and struggles, that's an obvious reason for weight loss. (Or weight gain in some other people like me who stress-eat.) On the day, remember not to eat if you're supposed to be fasting, but drink enough water to be well hydrated, so they can fill the vials they need for the tests. In the meantime, don't go looking online. Everything's cancer on the internet.