You’ve create a material that has mutliple levels of opacity and multiple reflective and refractive layers. This is going to look strange and take longer to render.
As Bmike suggests, get a glass material from Cosmos and save yourself the hassle.
You’ll need one labeled as “thin” if your glass has no thicnkess.
+2 here. No need to monkey around with the glass settings when there are several good glass materials in Cosmos to use as your starting point. Also make sure you have no Reversed Faces in your model. That can affect how materials, especially glass, renders.