I had two weeks off with gall bladder removal. I was in hospital a week before hand as i was very poorly and was given the standard two week sick note. Looking back I should have got another sickness note from GP as I really struggled on my return.
You need to seek medical advice. Remember if you are off for longer than 7 consecutive days (including weekend) you will need a sick note. The royal college of surgeons had advice leaflets on their website for many routine operations.