I Can Not Believe What I Did!

I don't often make a mistake but when I do it's a lulu. I started knitting this gorgeous long sleeve, tunic length pullover with some luscious plum coloured wool I've been saving for something special. With a 4mm circular needle I knit the four inches of k2, p2 rib around the bottom (in the round). Then I knit a further three inches in stocking stitch. At that point I thought I should make sure it was going to fit me so I slipped half of the stitches onto a 3 3/4mm circular needle, wrapped elastics around the ends of the needles so as not to loose any stitches and tried the sweater on. It did fit fine so I removed the extra needle and continued working stocking stitch, in the round, until the body of the sweater measured 20 inches (I'm long in the body). I thought I should try it on again, just to be on the safe side but when I picked up the spare circular needle I realized it was the size 4mm that I had removed from the stitches and except for the first seven inches I had knit the body of the sweater with the 3 3/4mm needle. I refuse to frog it. I am in the process of loosing weight and with luck and some dieting and exercise maybe it will fit me next winter. If not, I have a sister who might like it.