Sorry, Shortcake, sometimes I don't say everything I need to. Your fabric is 45" wide by 4 yards long (144"). So, if you cut two 18.5" strips from the width (total 37"), there's only 7" of usable fabric left of the width of fabric.
Another way to say it: you cut two strips 18.5" x 93, that totals 37" x 93", leaving a strip 7" x 93", plus the part of the length you haven't cut: 45" wide by 51" (144" minus 93").
Still clear as mud?!