Sir, My Sperm Is Sometimes Like Water And Sometimes Like

Sir, my sperm is sometimes like water and sometimes like jelly.before it used to be thick and pure white. And I continues of hair fall and I amnot gaining weight. I am 27 years old and only 55 kg with 175 cm height. Nowadays I using whey protein to gain weight. What might be the reason or cause for so and what will you advice me me for further medical treatment.