You should take levothyroxine with one full glass of water and that should do the trick.
I'm sorry you have after-operation symptoms so see your GP and if he thinks it necessary he will arrange for a scan. He will also look at your throat.
What dose of levothyroxine are you now taking? Has the GP increased it at all.
When you have a blood test it should be at the very earliest possible fasting (you can drink water) and allow approx 24 hours between last dose of levo and the test and take afterwards. This helps keep the TSH at its highest as it drops throughout the day and may mean the doctor doesn't adjust levothyroxine unnecessarily.
If you've not had a blood test for a while, make an appointment to have one and also ask for B12, Vit D, iron, ferritin and folate if these haven't been tested.
Always get a print-out of your results with the ranges for your own records and you can post if you have a query.