Exhausted/unwell after surgery

Hello
There are a bunch of frustrating things to read in your post.  Firstly, that your doctors think it's all so bloomin' easy and straightforward. It can take YEARS to get your thyroxine dose optimised and it sure as hell isn't as easy as "You weigh this and you're that tall so here, take 150 mcg a day". We are all different. How you take the tablets, what other medication you may use, even sometimes what you eat, can all make a difference. And you can meet big tall hefty people on less than tiny little wispy folk. 
How long it takes to get back to work depends on you - how well your body processes the anaesthetic, how well it adapts to the new medication (which takes up to 6 weeks just to stabilise), how well you handle pain and how well your scar is healing. Then throw in the fear and anxiety and it's not unusual for you to be feeling pretty terrible.

Be gentle with yourself. Ask your GP for a longer sick note and take your time. You had serious surgery and you won't necessarily just bounce back.

Two weeks is really quick to be back on your feet. I had surgery in may ‘20 and my thyroxine level is only just right. After surgery I struggled with emotions and fatigue and although I managed to go back to work after a month it has taken a long time to feel ‘normal’. This is a process that everyone goes through differently and you have to give yourself time. 
the first dosage check won’t be for 6-8 weeks. I will be surprised if you are at your final dose. Don’t forget surgery is traumatic and it takes time to physically and emotionally recover from that

Hi, can I ask how you are feeling now? I had my second operation 2 weeks ago as I had a part removal and then they advised I needed full removal so I have had 2 surgeries within 6 weeks, I am feeling the same as well as feeling low and not wanting to interact with anyone, the consultant also told me I would be able to return to work in 2 weeks. I was starting to feel anxious about returning due to struggling to wake and then the tiredness after only being awake for a couple of hours, I have spoken to the doctors and they have signed me off for another two weeks and ordered bloods before I see the consultant this week to discuss further treatment, and also to check if I'm on the correct dosage but they have advised me that they cannot change my dosage as they are led by the consultant and they also said it can take weeks for the medication to start working enough to notice a difference.