There can be several causes of increased hair fall, such as nutritional deficiency, stress, hormonal changes, exposure to pollution, and even dandruff. Diagnosing a specific cause needs some blood tests and other investigations.

Longstanding dandruff may be indicative of a skin condition known as seborrheic dermatitis. Dandruff and seborrheic dermatitis are fungal infections of the skin over the scalp. They make the hair weak and increase hair fall.

There has been much discussion about the side effects of excessive masturbation. However, there is no evidence that it is related to increased hair fall or other skin problems such as pimples. The practice, when done in moderation, is safe.

It is advisable for you to consult a dermatologist and take the appropriate treatment for hair fall. This may include a shampoo or lotion for dandruff and other supplements as required.
Also, note that it takes several months for hair fall to reduce. Remain patient and regular with the treatment for best results.

Reference
Borda, L. J., & Wikramanayake, T. C. (2015). Seborrheic Dermatitis and Dandruff: A Comprehensive Review. Journal of clinical and investigative dermatology, 3(2), 10.13188/2373-1044.1000019. https://doi.org/10.13188/2373-1044.1000019