You are going through an extremely difficult time physically and mentally and yet you work full time and eat well. You are a hero. Please do not be so self critical, what you are doing is wonderful. I am retired, thank goodness, I could not have worked even part time through chemo and radiation. I am still very tired and my brain doesn't work as well as it used to.
I agree with other people who commented, cancer does not respect anything. Even babies are born with cancer. It's not your fault you got cancer, it was your bad luck. Eating healthy food is a great idea, although sometimes chocolate is a life saver. Exercise is a great idea, if you have the energy for it. Maybe you could do a short walk at lunchtime, perhaps to buy a sandwich. Walking is great exercise for the body and the mind. you don't need to hit the gym necessarily. My oncologist recommended walking around shopping centers, they are flat, warm, dry, free and when you get tired you can sit down and rest. Eventually I am supposed to walk outside but to begin with, keep it gentle and safe.
I too suffered from much anxiety. I tried listening to guided meditations I found on the Internet. The ABC website has a stillness mediation I liked. I too have a monkey mind constantly thinking different things. I have read that this is fine, just observe the many thoughts you have and don't follow them. The point is not too have a blank mind, just not to mind the thoughts. I am not much good at mediation but it is definitely worth a try. The cancer society can send you a free cd with guided mindfulness medications in it.
I found a piece of music that I loved and listened to it a lot, it helped me feel less anxious. Mine was Pictures at an Exhibition but it would be different for different people.
A friend who had cancer finds listening to pod casts helpful for relaxing. There are many free ones in the Internet. Again the ABC website is a good place to start.
I agree, your oncologist has the most knowledge of cancer, follow his/her advice.
I suspect anxiety is very common with cancer sufferers. If medication works for you, talk to your oncologist about whether you should increase it. You won't be the first patient he/she has treated for anxiety. I discussed mine with my oncologist every visit. He was extremely understanding and prescribed Ativan. I could take it for a week after each chemo. I found it very helpful but did not enjoy coming off it. I had an unpleasant day and night, then the withdrawal was pretty much over.
I hope hearing that others experience anxiety helps you realise you are not weak or lazy. You are human. Anxiety sadly is very common in human beings. It's horrible but you will endure it in the the end. I learnt with cancer treatment, you don't have to like it, you just have to turn up and do it.
Wishing you the very best. Karen