Victims of domestic violence often try to keep the whole thing under wraps. They don't want to tell anyone what's going on. They dress in a way that hides the signs of physical abuse. They make up stories about their relationship so that it sounds healthy and safe when it's anything but. Friends have no idea what's really going on. Family members do not even know how far it's gone.
In some cases, people have a twisted view of the relationship. They think that they have brought the abuse on themselves in some way. They feel like it is their fault. They don't want to admit to it as a result, feeling like they have failed.
In other cases, they think that they actually deserve it. The abusive partner may tell them that they caused it with their actions or the things they said. They buy into this point of view and assume that everyone will blame them.
A lot of times, though, they just feel ashamed about what is happening. Everyone wants to have a successful, happy marriage. In the same way that failing business owners often act like their business is going perfectly, even as they near bankruptcy, someone who is abused may keep lying just to protect this public image. They want people to think that they're happy, so they act like they are.
Don't do this. It's very dangerous and only makes the situation worse. Remember that this is not your fault, and it's nothing to be ashamed of. You need to tell people and look into the legal options you have to protect yourself.