Why is transformer flux constant?

When a load is connected to a transformer current (say I2) flows through secondary coil thus an M.M.F (N2I2) is produced, this produces the secondary flux. This flux reduces the main flux induced in the primary & also reduces E.M.F E1 in the primary. As a result more current is drawn from the supply. This additional current drawn is due to the load component I2’ .This I2‘ is anti-phase with I2.This I2‘ sets a flux which opposes the secondary flux & helps the main flux. The load component flux neutralises the secondary flux produced by I2 .The M.M.F N1I2balances N2I2.Thus the net flux is always at constant level