How long would it take to flush THC from your system if you smoke a bowl about two times a week for the last three months?

Basically, you smoked a lot, so it will take ages.

THC is fat-soluble but not water-soluble, so it is not cleared well by the urinary system. Instead it remains stored in fat cells in the body until those cells are burned for energy, releasing the stored THC.

Given the amount smoked, you would not be clean for about four weeks, unless you somehow manage to burn every trace of fat from your body (which is pretty much impossible) and were to drink dangerously excessive amounts of water every day (which would probably put you in hospital) for days on end.