I'm feeling pain over the last few weeks in the left side of my lower abdomen whenever i masturbate, i try to delay ejaculation to extend pleasure.

Lower abdomen: It is likely there is strain of testicular structures or build up of excessive congestion and or irritation/mild inflammation of testicle or epididymis. Irritation/inflammation in the testicular area can cause referred discomfort in the lower abdomen and groin. I advise reducing masturbation and let things settle down. See your physician or a urologist if discomfort persists.