they sliced through your bladder?
have you been to see another doctor instead?

common causes of pain months post operation are incorrect healing and/or adhesions.

it sounds like you had an abdominal hyst.
you should have been instructed to refrain from lifting and to only do light walking for 6 weeks, then to start slowly increasing your lifting and exercise over a 12 week period.

not allowing correct healing at that point often leads to problems later down the line.

if the sliced your bladder there is likely to be scarring on the bladder and I would question if they have damaged your bowel also.

scarring on the bladder and/or bowel along with pushing to fast in the recovery period often lead to adhesions.
that is strip of scar tissue that form - effectively sticking the internals together.

your first step is to be examined by a different doctor as there are numerous reasons for the pain (those I mentioned are the most common but also the least worrying).