gluUnproject gives non-logical values (C++) - c++

Question

I'm currently working on a project, and I need to be able to move objects with my mouse, and to do some mouse picking. I generate a 1024*768 window, and my code with gluUnproject is :
glm::vec3 GetOGLPos(int x, int y)
{
GLint viewport[4];
GLdouble modelview[16];
GLdouble projection[16];
GLfloat winX, winY, winZ;
GLdouble posX, posY, posZ; // posX2, posY2, posZ2;
glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
glGetDoublev( GL_PROJECTION_MATRIX, projection );
glGetIntegerv( GL_VIEWPORT, viewport );
winX = (float)x;
winY = (float)viewport[3] - (float)y;
glReadPixels( x, int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ );
gluUnProject( winX, winY, winZ, modelview, projection, viewport, &posX, &posY, &posZ);
std::cout << "PosX = " << posX << " - PosY = " << posY << " - Pos Z = " << posZ << std::endl;
return glm::vec3(posX, posY, posZ);
}
And I use it this way :
glm::ivec2 pos = _input.getMousePosition(); //0, 0 is high left corner
glm::vec3 posIn = GetOGLPos(pos.x, pos.y);
The position in pixels are good, but the position I get are, I think, false.
Here is some output I have if I click in the center of the screen (My object origin is in (0, 0, 0)) :
Xpixel = 512 Ypixel = 364 XOGL = 0 YOGL = -0.0111111 ZOGL = 1
And the output I have when i click somewhere else :
Xpixel = 237 Ypixel = 207 XOGL = -0.537109 YOGL = 0.425 ZOGL = 1
So I have two problems here :
The Z value doesn't change (so maybe it is a vector and not coordonates)
The object moves toward my mouse (since I translate my object to the new coordonates, so the new origin point should be XOGL, YOGL, ZOGL) but only on few pixels. So the values are either wrong or misused.
Can someone help me?