hi.. i have understood your concerns...
first of all, dont worry u do not have any serious sex disease..whatever happening to you is because, u stopped masturbating for 1 year and u are not married, dont have girl friend.. so what will happen to your semen, because it is continuously produced, and the sexual glands have become full of it...
so whenever u have sexual excitement and erection, during night when penis becomes hard, during passage of urine and stool when intra-abdominal pressure rises..it comes out without any sexual activity, its a simple physiology..
its a normal phenomenon..there is nothing to worry.. if u want to stop it , then start masturbating thrice weekly or the best is get married..
masturbation is not a bad habit and nothing shameful in practicing it..do not believe in myths that are prevalent in the community about sexual problems..
it is good that u go for exercises regularly and continue that..
i hope u ll find this advice helpful.. best luck..