So sorry you are feeling this way. I haven't finished treatment yet but 1/2 way through chemo my anxiety levels went through the roof. I didn't know what was wrong with me. Things that normally would worry me, ie needles, were freaking me out. It turned out that I was suffering depression as well as high levels of anxiety. I'm now on medication and seeing a counsellor, both of which has helped tremendously. I actually don't think it is unreasonable for you to be feeling this way. Let's face it, none of us want to go through any of this every again but unfortunately there is a percentage of us who will.
Get some professional help. Life is too short to be unhappy and worrying about things that might not even happen. I hope it eases off for you and that you are able to enjoy the new year. Xox Karen