For goodness sakes young lady...that is a lot of work, and discomfort to accomplish fake breasts.
I have no idea how old you are, but if you are an adult you can buy locally,or catalog order, soft realistic looking and feeling fake breasts that can be put into a bra. No need to draw down a strap/belt on yourself either.
My first attempts at making breasts, was I put on my older sisters training bra, and nylon socks into it. I put my sweater back on and went to show everyone. I think I was 8 or 9. At first they laughed, then my sister got really P.O'd. She and my Mom told me not to do it again...I remember I liked it...what can I say?