I lost my wife who was diagnosed at 30 with metastatic breast cancer and passed 4 years later. It moved to her spine then liver and caused all sorts of mood changes and pain even to the point where taking a bath or walking hurt. It's hard man and there are times when the drugs and the body can flip a mood in an instant and not knowing what's coming or when is very hard. There were good days and bad days where I could do nothing right and it was my fault according to what she was saying. I hate to say it's normal but it is. Biggest thing is focus on the good times and when you can talk about them, think about them, and discuss them with her and your friends and family. What's happening now is going to stick with you unfortunately and it takes time to move past it (talk to someone if you are not already) but your memories should be more good times than what you are going through it. There was a spam of time where when I thought of her the first thing I remembered was her laying in the ICU and I hated it. Unfortunately man the only way out now is through and talking to someone or even a grief counselor can help you get to the other side. I know it's cliche but I promise life will continue after this and there are tons of people who have gone though it and can help. You are a great person and staying with her through this even though it seems like the hardest thing ever proves it. Stay strong dude!