From re-reading what you've written in your opening post, I just want to make sure you're doing the yarn overs correctly. That's the only reason I can think of for your coming up without enough sts.
A yarn over is simply wrapping the yarn around the needle - after you knit your 2nd st, bring the yarn to the front between the needles, then to the back over your right needle. Knit your 3rd st, which has now become the 4th st in your count.
I'm sorry if you know that and I'm wrong, it's just the way I could account for it not adding up.
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