Hello- Yes it is due to masturbation. Put simply, over-masturbation will lead to sexual under-performance by way of premature ejaculation, as well as other sexual problems. Normally, masturbation is a healthy sexual behavior. And like other behaviors, over-indulgence can lead to both psychological and physiological imbalances. Frequent masturbation and ejaculation will stimulate the acetylcholine along with the parasympathetic nervous functions, so you are facing such involuntary ejaculation. However it can be cured by strengthening the nerves and reducing the sensitivity of the penis by the help of herbal medicines of Ayurveda.