Relax. Take a deep breath and relax.
What will be most important to you and your guests on your wedding day won't be the colors. It will be the huge smiles on your face and your husband's face and the joy you both radiate.
That said...if the dress is stressing you out and you can't get over it, see if you can exchange it for something that better suits you.
FWIW, I think alabaster and red would look fine together.