How do i keep cheerful

My husband has stage 4 bowel and liver cancer. He has had chemo, surgery and radiotherapy. He is 74 and I am 70. He needs to have two major surgeries in the near future. He is physically well and still working part time. He’s very upbeat and positive but I am struggling as he wants me to be happly and jolly all the time. He mocked me in front of his consultant because I cried in one of his appointments and she made a joke of it too.I feel like I am under constant pressure to laugh and joke around about his cancer when I feel overwhelmed. I already suffer with depression and am having treatment for it but this has been going on for almost 2 years and I am exhausted trying to keep up a happy jokey front. Is there something wrong with me and how can I manage my feelings as he says I’m not helping him.