Hi Sandra,
I have just finished 6 rounds of chemo and worked right through, with sick days as needed, it kept me sane and my brain continued to work, although my memory is crap right now.
My original job involved on call work so I adjusted this to an area which was easier to manage.
I would think a new job and with such long hours that you are doing, would be exhausting and maybe as you have asked the question, it is too much at the moment. Having said that, it may get better.
I agree with what others have said to listen to your body.
Good luck xx