Kyrie,
First off thank you so much for your question, and I will do my best to try and help you out. Now, I know this must be a very hard thing to deal with. I'm going to give you a little background on me, so you can understand where I'm coming from. When I was nine years old I lost my father to skin cancer. He had been fighting it for most of my life, and I know exactly what those doctors appointments are like. It's hard for everyone involved. Everyone has so many different questions and feelings, and many times don't quite know how to deal with all of this.
The best advice that I can offer you, is to be open with everything that you are feeling. I know the only thing that got me through my hard times was staying close and open with my family. It's a very helpless feeling, because unfortunately there isn't anything we can do to make the disease go away. All you can do is continue to be open, and be there for your boyfriend. Think about how scared you are right now and then think about how scared HE must be as well? I'm sure that he is going to need you through all of this, and It really sounds like you're going to need him to get through it too.
Remember also, that it's okay to be scared. It doesn't do anyone any good to keep everything inside and try to hide it. It's okay to be scared, and it's okay to cry. Just be as open as you can and try to be there for all of those around you. Hopefully, they will return the favor and you can all band together.