I have done stapler haemorrhoidpexy recently last...

What is the treament of Piles ?
Your condition may be due to failure or incmpleted surgery , or maybe it's due to recurrent Piles , so it's important to consult your surgeon , until this you have to follow some instructions such as drinking as much water as you can and eating alot of fiber sources toprevent costipation , warm bath also could a good choice for your condition if daily applied , doctor will prescribe you some medications such as hemorran cream and daflon as well as antibiotic such as flagyl in case of infection  till you're ready to undergo another surgery 
What is the investigations needed for Piles ?
Clinical assessment for your case is enough to diagnose and evaluate
What are the manifestations of Piles ?
Pain 
swelling
Bleeding 
chronic Constipation
Itching
Advice :
you have to re-consult your sugeon who did the operation