Why does my boyfriend's dog hate me?

Question

My boyfriend's dog hates me and I don't know why. He is fine when others are around, but when I'm alone he gets really aggressive towards me. Here is an example of his behaviour towards me this afternoon:

He started scratching at my room door, so I went to check if he wanted water or to go outside; I let him out and waited for him at the door. He charged back in and ran past me and started acting strange by making weird defensive poses and barking; he then comes back to me and starts viciously barking at me, growling at me and coming towards me as if he is going to attack me. Sometimes he is foaming at the mouth with rage. If course, I am terrified by this point and shut myself outside and he keeps barking at the door until he is bored.

It usually happens in this pattern, and sometimes I am shut out for hours before he stops (or someone comes home). I have been living here for about 6 months and these situations happen almost every day. It mostly happens after I let him out, but there are a few times he has done it randomly, and a few situations in which I have no escape. But he has never bitten me, but I think it is only because other people stopped him barking at me.

This is very stressful and emotional problem, I hate having to sneak around the house past him and well just being scared all the time of dying is not nice. Please help.

Edit for more information:
He is a 10 year old Shar-Pei called Diesel, a family pet of my bf since he was a puppy, and he does not behave this way to others, even those who are newer to the house than me.

Answer 1

Expanding on my comment --

It sounds to me like at least part of your problem is that you have not asserted yourself as being higher ranked in its "pack" than the dog. When you have nervous body posture, or flee from the dog, these look to it like signs of submission. The natural response for a more dominant dog to acts of submission is to start acting more dominant. And so due to this cycle of aggressive behavior, and your appearing submissive, it now thinks it's higher ranked than you.

As I said in my comment, a sharpei is a fairly large dog, certainly big enough to cause harm if this were to escalate further, and so these patterns of aggression are definitely not a good thing. I recommend you get a trainer, especially one that can come to your home and observe the problem first hand. The trainer I think would be especially good for you, as they can help teach you how to interact in general with the dog to establish your dominance, and get over your fear of the dog.