You're 19, and therefore able to take your own decisions about your sexual preferences, and I'm sure your father will respect that. But he will naturally be worried about you and will want to know what the situation is and want to offer his advice. I would avoid telling him that this is an undying obsession of yours that you cannot live without, but rather, that it is something that you find a turn-on, and you have come to realise that you are not alone in this, but that a vast number of people are into this as well. Explain that it has been a real relief to you to realise this, and you are therefore interested in finding out more about it on the internet.
Explain how this fetish has affected your ability to relate to the oposite sex, but again in such a way as to hint that things are reasonably normal there. (Parents are often worried about this issue) If he has come across scenes of heavy bondage or other, more hardline stuff, don't say that you regularly indulge in this sort of thing, and get your ideas from the internet, but again, play it down, explain that it is interesting but doesn't really affect your life.
Altogther, he will probably be most open to a reasonable, honest approach, one where you do not start by becoming defensive and making exuses which will enable him to trap you in contradictions. If you stand up for what is true and right for you with a certain confidence, without being cocky, you have probably won your point. If he is a conservative who believes all this stuff is evil and will determine your long-term future in hell, then you may have to change your approach a little.
This is a start. Should it be of any use to you and you want to ask more, either PM me or continue to ask on this thread, where others can join in.