Hi there ~
Nightfall or nocturnal ejaculation is not abnormal. Some men have the physiological phenomenon and some do not. However if doing yoga
is resolving the problem to any extent I advise you to continue the same, as it has other benefits as well. The white discharge is an unclear thing and you might need a urinalysis
and a semen analysis
if you continue to have pain or burning sensation when you are having this issue. I hope you visit with a psychiatrist
who can better help you by examining and taking a good history.
Take care and have a lovely day!