I'm sorry to hear your news and how hard you are finding it.
Diagnosis in March and all that surgery with chemo started in May has been quite a busy few months.
I am two months ahead of you but with lesser diagnose, surgery and treatment and I've only been able to think normally about everyday life for the last few weeks. Since radiotherapy finished I guess.
Don't beat yourself up about feeling angry or any other emotion you have, whenever. I think we have all experienced the same and to not feel that way would be unusual. It takes time but eventually the continual thoughts about cancer start to subside and emotions even out.
Till then be gentle with yourself and I wish you well through chemo. (I've been there done that, 9 doses over 6 months, 22 years ago)