Hi NeeNooksDH and welcome - so sorry you have been through this horrible illness, I can't help much about the work, - I haven't returned to work since my DX. But perhaps I can offer a bit of support about the fatigue.
With me and with lots of people the fatigue went on long after the treatment had finish, and I was told by various medics to expect fatigue and after effects to last at least as long as you were in treatment. If you had chemo and radiotherapy as well as your surgery add on even more time. It sounds as if your surgery was pretty major 
- that is a hell of a lot to go through, especially having to cope with the physical adjustments as well as all the emotional things.
You also say you worry about the cancer coming back - I'm sure that's something we can all sympathise with on here - and it is emotionally exhausting. But I can say that the longer the time you stay well the easier it gets on that front.
Back to fatigue. I think cancer/treatment fatigue is very hard for those around you to understand - they think it means the same as 'tired' which of course you will know doesn't come close!
Firstly - acknowledge it is there, don't try to ignore it, or battle through it.
Next I would say pace yourself, initially I found for every 20 mins activity I needed a 20 mins break, but small chunks of work were easier to cope with. Now I realise that is hard in a work environment, but it might be worth talking to those in charge about what can be done to help you make the most efficient use of your day with some recovery time built in for you.
It's demoralising because it feels never ending, but it will be improving just by very small amounts. So it might feel as if you are getting nowhere. It was suggested to me that I keep a notebook or diary, just quickly noting each day what I did and how I felt (exhausted, or not too bad whatever) after a few weeks you can look back and see that you are actually making some progress and getting stronger.
What has happened to you is a big deal, and you are entitled to have all sorts of feelings about it, - we often say to each other on here that this thread is for a good rant or moan if it helps, or a cry on occasion. I have a cry about it all in the bath or shower sometimes - just to get it out of my system a bit without panicking my family! 
I'd also suggest get help and support wherever you can. MacMillan are excellent - they have helplines, - I've found them brilliant for talking about these sort of feelings, and for giving really good practical ways you can help yourself through it. I think they also have booklets on their website on very specific topics, fatigue and return to work are likely to be there.
Cancer support centre, if you have one nearby, often have loads of info and experts on fatigue, getting back to work and so on. IME men are sometimes reluctant to access some of the support (I don't want on any way to sound patronising saying that) but it can be hard - I know my DH would find it difficult. But also IME there are plenty of men who do go to support centres and find it very helpful. Definitely worth asking at your hospital or asking your nurse specialist if you have one what is available.
I hope some of this long post has been helpful. You are very welcome here, as of course is your DW if she wants to pop on.
much love to you both xx
Loads of love to other ladies today, I hope everyone is OK, - MAS hope things are OK with your friend
sorry I haven't been on - a combo of me feeling wiped out and falling asleep all afternoon 
and my computer making a noise like Concorde taking off with some extra grinding sounds thrown in for good measure. So have to keep turning it off. I think its the fan????
love to all - will try to post later when I've had my tea.