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The semen you are talking about if it is watery clear in color then no reason to worry as it is the prostatic fluid produced by prostate
gland in your body and is necessary for lubrication during sex.This fluid comes out on every time you get excited and will not harm you.As for semen it usually is discharged at time of orgasm and you will get a feeling of pleasure at that time.So first of all you need to differentiate the two.As for the burning it can be as a result of internal infection or injury
due to friction if you are trying hard to control your erections.If the burning increases please consult a doctor near by and he will help you with the treatment.Ejaculation also occurs due to over excitement so do not worry first get married and hopefully things will settle.If you have trouble after marriage then you will have to consult a Urologist
but i guess it will not be necessary.