Your current problem is "Night Falls" (ejaculation without sex during sleeping) which is quite normal. For this,your pant is wet with semen. It occurs occasionally and not regular basis.
**CAUSE: 1) much thinking about sex and pornography 2) indigestion
**GUIDELINE to AVOID "NIGHT FALLS":
1) Try to busy yourself in work or other things
2) keep mind always fresh and don't think much about sex
3) Meditate regularly for 15-30 mins
4) take healthy diet and keep stomach clean always
5) do light exercise with clean your private parts regularly.
I think you will be benefited more with above things.
All the best.