It sounds as though you have pericoronitis of the lower left wisdom tooth. This is an infection caused usually by food trapping and bacteria build-up underneath the gum flap covering the wisdom tooth.
The white liquid you can express from the infected area is pus, which is a combination of bacteria and dead white blood cells fighting the infection.
Since you have already had 2 episodes of infection, it would be a good idea to consider removing the wisdom tooth to get rid of the food trap once and for all.
Removing such a tooth will also help prevent decay and gum infections affecting the adjacent molar in the future.
