hi, thanks for writing. i have understood your concerns. the fluid which comes out after erection is not semen. it is prostatic fluid which is also called as precum or pre-ejaculation fluid. it does not contain sperms. it is normal phenomenon and occurs with every one..so you shudnt worry about that. the early ejaculation of semen is common problem among the males practicing masturbation. as such masturbation does not cause this, but it the way of masturbating in hurry with rapid strokes, excessive stimulation..all these causes a behavioral conditioning which result in to early ejaculation every time person masturbates. whenever there is a transition from masturbation to sex, this also occurs there. If you really want to delay your ejaculation time then decrease the frequency of masturbation if you are doing it repeatedly. there are method of delaying ejaculation without taking drugs. these methods are behavioral techniques: squeeze method, stop-start method and other interruption method. you can read them from internet. drugs are also available which can delay the ejaculation time. for all these i insist that you shud consult a sexologist and ask for help. take information about sex and foreplay. the normal ejaculation time is 3 to 7 minutes more than 30 minutes of erection without ejaculation is dangerous. I hope this advice will be helpful to you,..best of luck..