The cycle of scans, waiting, scans, waiting can be a difficult one. I'm on a 3 month cycle too. I generally think that I handle it well, but after a scan I do feel the relief. So, I know I'm not entirely honest with myself about how I'm feeling during the lead up to scan day too. The people around us, just want us to be ok so it's not always easy to talk about how we're feeling. It's normal to feel isolated. We're alone with the heaviness of our thoughts. I try to work through the feelings, and don't allow myself to sit in that place for too long. Talking with someone can be helpful.
You may want to reach out to your care team, a social worker or palliative care member, they may be able to help in finding ways for you to work with the waves of depression.