I'm having very strong headaches on the left side of my head, what could be causing them?

Several reasons: There are several reasons behind the occurrence of head pains ranging from genetics, muscle contractions, stress, sleep disorders, teeth grinding, trauma, and different medical illness. The exact causes of headaches aren't known. You could try some self care strategies like massages, warm compresses over neck/temples, green tea, relaxation, and ibuprofen/tylenol.

Different causes: There are so many different causes of headaches such as migrane, tension, tumors and etc. You should not be guessing but see a neurologist and find an answer.