Why does it feel like i physically NEED a hug?

Let me start off by saying that my father died a year and a half ago when i was only 13, almost 14. He did give me hugs pretty much everyday, like any father would hug his daughter. I'm not sure if thats part of my problem or not. Lately, ive been feeling like a physically NEED a hug, like i just want one so bad. I know what you're thinking; what about ur bff? Well, the truth is that while we do have a good relationship and we tell each other everything, we've only hugged once when i was really upset and crying. I just chalk it up to that she's not a physical person, which i understand. But I on the other hand, love hugs. But i havent been getting many. So my question is; why do you think i feel like i NEED to have a hug, and what is it about the human touch that makes us feel like we NEED it so bad (is there like a science to it or something)?