@Mic80, it's probably an accumulation of all the factors you have mentioned, plus the emothional response to all you are going through, physically & emotionally. Have you considered some counselling? The BCNA helpline might be a good place to start for some suggestions on where to go for help and support 1800 500 258, predominantly business hours. Is that right @Giovanna_BCNA? The Cancer Council also have a line, 131120.
My local cancer centre also has counsellors available to us, check with your hospital what may be available to you.
Let your team know how you are feeling, they need to know and they can't know unless you tell them.
Above all else, let those closest to you know how you are feeling, they'll want to help, love and support you.
What you are feeling isn't unusual, in fact many who have been treated for cancer end up with a form of post traumatic stress, which is why it is so important that you continue to reach out for help and support. This stuff is HARD!!!!
Take carw, I'll be thinking of you