I can understand your concern. It appears to be a problem of premature ejaculation. Nocturnal discharge is a common presentation. With suitable medications and instructions it can be completely cured. Although, stress and anxiety are two major risk factors for premature ejaculation problem, in many cases there may not be any specific cause to it seen.
Next Steps
I would suggest you to consult with a sexologist. For more information regarding this problem and advice on management you can consult me directly here on practo.