When I am practicing hold back by myself, almost always around 15-20 minutes some semen escapes, without really ejaculating or anything like that. Like how they teach you in health class that semen can be emitted before "orgasm"...hah, well is this bad? If so how can I avoid this. I've been practicing this for only a few weeks, maybe 6 or 7 weeks now. Thanks.
If it is really semen, then I suggest to stop tantric practice for some weeks (3+) and remain celibate, so that the prostate may "normalize". Only then, start a regimen of kegel exercise for some weeks.
When kegel become second nature, you can try again tantric exercise and see what happens.