Wellll.... are all the YOs too loose, or just some? If just some of them are, are they before or after decreases or purl stitches or what? Usually a YO between a knit and purl can be loose if done `correctly', which is bring yarn to the front, over the needle and to the front again, which makes it half a wrap more, kinda. You can change that by just bringing it over the top too the front loosely to purl, but remember it's done backwards so on the next row, you have to knit into the back leg of it or it will be too tight and twisted.
Also, it may not be as bad as you think. Try blocking it while it's still on the needle, or put it on scrap yarn, and see how it looks then.