I can sew, though I kind of stopped since I don't want to wear the kind of clothes I want to make.

What I have to say is it will be a lot harder to fit something to yourself than to another person, so you should have someone who knows to assist you. They have to know what they're doing to pin it right when you're doing alterations.

And if you want a great dress, learn to make patterns. You will get a better fit than if you altered a pattern, and the knowledge will make you able to sew it with more skill when you know exactly what is going on. How soon is your wedding?

Edit: Oops, I see you decided not to do it? Don't give up, sewing is fun. Make things other than wedding dresses.