This is a normal reaction. You can try to control your sexual urge, or even ejaculation/ leakage, by doing deep breathing or abdominal breathing. Do it 10 minutes twice a day. Google abdominal breating, read it and practice it. and when ever you feel urge, take deep breath. Just will power will not work. By practicing slow deep and even breathing you can control all types or urges.Seamen is produced every day. So If you do not masturbate it will go out by way of ejaculation. Practice of deep,slow and eve(inhaling and exhaling timings are same).You may not completely stop ejaculation. So try to reduce frequency and do not worry about night falls.
You might check with a Catholic expert or website, but celibacy is not defined as never having an accidental nocturnal emission, as those are beyond your control. The word "celibacy" refers to deliberately refraining from sexual acts. Certainly things that happen in your sleep by accident can't be considered a breach in your vow to stay chaste. Here is from one Catholic website: "To be a sin, it must be committed with full knowledge and deliberate consent." I realize you are not asking if this is a mortal sin, but it should help you see that when it is an experience over which you have no control, it is not a sin. You've gotta do it on purpose.
Taoists have solved this problem by converting sexual energy by circulating awareness around orbit of governor and functional channels.It is converted to mental energy and from mental to spiritual energy. If one does not want to go further one can control sexual urge by abdominal and deep breathing.