Hi Doctor, I Have A Problem With My Sperm. At

Hi Doctor, I have a problem with my sperm. At first everything was okay and I have been masturbating about 10years now. My sperm was thick all along, things started to change on the 7th year of masturbating and it was an everyday thing, I couldn't skip a day without doing it. Now I'm experiencing watery sperm, the color is fine nothing has changes. How can I make my sperm to be thick as before without taking any drug and how long it will take?